{"Bibliographic":{"Title":"Benthic invertebrates and sediment characteristics in Wahkiakum County Ferry channel, Washington, before and after dredging","Authors":"","Publication date":"1996","Publisher":""},"Administrative":{"Date created":"08-16-2023","Language":"English","Rights":"CC 0","Size":"0000044331"},"Pages":["SH153\nUn515e\nBenthic invertebrates and\nsediment characteristics\nin Wahkiakum County\nFerry Channel, Washington,\nCZES\nbefore and after dredging\nby\nCoastal Zone and\nGeorge T. McCabe, Jr.,\nEstuarine Studies\nSusan A. Hinton,\nDivision\nand Robert L. Emmett\nNorthwest Fisheries\nScience Center\nAugust 1996\nNational Marine\nFisheries Service\nSeattle, Washington\nScience","Narsen\nBENTHIC INVERTEBRATES AND SEDIMENT CHARACTERISTICS IN WAHKIAKUM\nCOUNTY FERRY CHANNEL, WASHINGTON, BEFORE AND AFTER DREDGING\nSH\n153\nUn5ise\nby\nGeorge T. McCabe, Jr.,\nSusan A. Hinton,\nand\nRobert L. Emmett\nFunded by\nU.S. Army Corps of Engineers\nPortland District\nP.O. Box 2946\nPortland, Oregon 97208\n(Contract #96930051)\nand\nCoastal Zone and Estuarine Studies Division\nNorthwest Fisheries Science Center\nNational Marine Fisheries Service\nNational Oceanic and Atmospheric Administration\n2725 Montlake Boulevard East\nSeattle, Washington 98112\nAugust 1996","","iii\nEXECUTIVE SUMMARY\nIn 1993, the Portland District of the U.S. Army Corps of Engineers contracted with the\nNational Marine Fisheries Service to study benthic invertebrates and sediments in the\nWahkiakum County Ferry Channel, Washington (River Mile 43.2), before and after dredging.\nAlthough the area of the dredging project was small, there was concern that benthic\ninvertebrates, particularly the amphipods Corophium spp. (C. salmonis and C. spinicorne),\nwould be adversely impacted. Corophium spp. are abundant in intertidal and shallow subtidal\nhabitats of the Columbia River estuary and are seasonally important in the diets of juvenile\nsalmonids and other fishes. The goals of the study were 1) to describe benthic invertebrate\ncommunities in the dredged portion of the ferry channel before and after dredging and 2) to\nassess recolonization of benthic invertebrates in the dredged portion of the ferry channel. We\ncollected samples in a control area located about 3.2 km (2 mi) upstream from the ferry\nchannel to help assess the effects of dredging. Specifically, we assessed benthic invertebrate\nspecies composition, standing crops, diversity, and equitability in both the ferry channel and\nthe upstream control area.\nBenthic invertebrate and sediment samples were collected with a 0.1-m2 Van Veen\ngrab sampler at seven stations in the Wahkiakum County Ferry Channel and at an upstream\ncontrol area in October 1993, January, February, April, July, and October 1994, and January\nand April 1995. Sampling in October 1993 and January 1994 was conducted prior to\ndredging in the ferry channel, and sampling in February 1994 was conducted 6 days after\ndredging was completed. No significant effect (P > 0.05) of the ferry channel dredging\nproject on benthic invertebrate densities (total) was detected in the statistical analysis,","iv\nalthough benthic invertebrate densities were significantly different (P < 0.05) between surveys\nand areas. Benthic invertebrate densities were significantly higher (P < 0.05) in the control\narea than in the ferry channel.\nDuring all eight surveys, Corbicula fluminea, Corophium spp., and Ceratopogonidae\n(Diptera) larvae were generally the most common benthic invertebrates in both the ferry\nchannel and the control area. No significant effect (P > 0.05) of the ferry channel dredging\nproject on densities of Corbicula fluminea, Ceratopogonidae larvae, or Corophium spp. was\ndetected in the statistical analysis. However, densities of Corbicula fluminea and\nCeratopogonidae larvae were significantly different (P < 0.05) between surveys and areas,\nwith densities significantly higher (P < 0.05) in the control area than in the ferry channel.\nCorophium spp. densities were significantly different (P < 0.05) between surveys, but not\nbetween areas.\nTwo measures of community structure, Diversity (H) and Equitability (E), were\ncalculated for each area for each survey. No significant effect (P > 0.05) of the ferry channel\ndredging project on the benthic invertebrate community structure, as measured by H and E,\nwas detected in the statistical analysis. Both H and E were significantly different (P < 0.05)\nbetween surveys, but not between areas.\nThree sediment characteristics--median grain size, percent silt/clay, and percent volatile\nsolids--were determined and compared for each area and survey. No significant effect\n(P > 0.05) of the ferry channel dredging project on median grain size or percent volatile\nsolids was detected in the statistical analysis. Median grain size was significantly smaller in\nthe ferry channel than in the control area (P < 0.05). No statistical comparisons for percent","V\nsilt/clay were made because of the non-normal distribution of the data and the lack of an\nadequate data transformation.","","vii\nCONTENTS\niii\nEXECUTIVE SUMMARY\n1\nINTRODUCTION\n2\nMETHODS\n2\nSampling\n4\nData Analyses\n4\nBenthic Invertebrates\n5\nSediments\n5\nRESULTS\n5\nBenthic Invertebrates\n15\nSediments\n20\nDISCUSSION\n25\nACKNOWLEDGMENTS\n26\nREFERENCES\n29\nAPPENDIX","INTRODUCTION\nIn 1993, the Portland District of the U.S. Army Corps of Engineers (COE) contracted\nwith the National Marine Fisheries Service (NMFS) to conduct benthic invertebrate and\nsediment studies in the Wahkiakum County Ferry Channel, Washington (River Mile\n(RM) 43.2), before and after dredging of the channel. The Wahkiakum County Ferry, which\nis owned and operated by Wahkiakum County and subsidized by the State of Washington,\noperates between Westport, Oregon, and Puget Island, Washington. Prior to the NMFS\nsurveys, shoaling in the ferry channel between Puget Island and the main navigation channel\nof the Columbia River forced the ferry to operate at one-half capacity during part of the year\n(U.S. Army Corps of Engineers 1992). Clamshell dredging was conducted in about 244 m\n(800 ft) of the ferry channel, from 24 January to 17 February 1994. About 14,258 m³ 3\n(18,650 yd3 of sediments were removed from the channel and disposed of at an in-water\ndisposal site about 4 km (2.5 mi) downstream from the ferry channel. Although the ferry\nchannel is about 579 m (1,900 ft) long, only about 244 m (800 ft) had to be dredged, as the\nremainder of the channel is naturally deep. The ferry channel is 61 m (200 ft) wide.\nAlthough the area of the dredging project was small, there was concern that benthic\ninvertebrates, particularly the amphipods Corophium spp. (C. salmonis and C. spinicorne),\nwould be adversely impacted. Corophium spp. are frequently found in intertidal and shallow\nsubtidal habitats of the Columbia River estuary and are seasonally important in the diets of\njuvenile salmonids and other fishes (McCabe et al. 1983, 1986; Kirn et al. 1986; Muir et al.\n1988). Corophium salmonis and C. spinicorne were the dominant prey for juvenile salmonids\ncollected during the spring of 1984 at Bonneville Dam, the lowermost dam on the Columbia\nRiver (Muir and Emmett 1988).","2\nThe goals of the present study were 1) to describe benthic invertebrate communities in\nthe dredged portion of the ferry channel before and after dredging and 2) to assess\nrecolonization of benthic invertebrates in the dredged portion of the ferry channel. We\ncollected samples in a control area located about 3.2 km (2 mi) upstream from the ferry\nchannel to help assess the effects of dredging. Specifically, we assessed benthic invertebrate\nspecies composition, standing crops, diversity, and equitability in both the ferry channel and\nthe upstream control area. Results from the present study will provide useful information to\naquatic resource agencies who assess the potential environmental effects of dredging in\nsimilar habitats of the lower Columbia River.\nMETHODS\nSampling\nBenthic invertebrate and sediment samples were collected at seven stations each in the\nWahkiakum County Ferry Channel and an upstream control area in October 1993, January,\nFebruary, April, July, and October 1994, and January and April 1995 (Fig. 1). Sampling in\nOctober 1993 and January 1994 was conducted prior to dredging in the ferry channel, and\nsampling in February 1994 was conducted 6 days after dredging was completed. Sampling\nstations were located using a radar range-finder and the Global Positioning System (GPS)\n(Appendix Table 1).\nAt each of the 14 stations, a 0.1-m2 Van Veen grab sampler was used to collect four\nsamples; three were analyzed for benthic invertebrates and one for sediment type. Each\nbenthic invertebrate sample was initially preserved in a buffered formaldehyde solution (>4%)\ncontaining rose bengal, an organic stain. Later each benthic invertebrate sample was washed","of the Wahkiakum County Ferry Channel, Washington, and the the upstream channel control and area. control Locations area are shown of benthic in\nWC14\nNC13\nWhite Island\nWC12\nWC11\nWC10\nWC8\nWC9\nWashington\n1. Locations and sediment sampling stations in the dredged portion of ferry\nColumbia River Channel\nPuget Island\nWahkiakum County\nFerry dock\nOregon\nW6\nW7\nW4\nW5\n.\nW2\n.\nW3\n1,000\ninvertebrate\nW1\nthe insets.\nWashington\nOregon\nMeters\n500\nN\nFigure\n0","4\nwith water through a 0.5-mm screen. All benthic invertebrates were sorted from each sample,\nidentified to the lowest practical taxon, counted, and stored in 70% ethanol. The sediment\nsample from each station was placed in a labeled plastic bag and refrigerated for analysis of\ngrain size, percent silt/clay, and percent volatile solids by the COE North Pacific Division\nMaterials Laboratory, Troutdale, Oregon.\nData Analyses\nBenthic Invertebrates\nBenthic invertebrate data were analyzed by station to determine species composition,\ndensities (by taxon and total), and community structure (diversity and equitability). The\nShannon-Wiener function (H) was used to determine diversity (Krebs 1978), which was\nexpressed as:\nS\nH = - (p))(log2p)\ni=1\nwhere p = n/N (n is the number of individuals of the ith taxon in the sample, and N is the\ntotal number of all individuals in the sample) and S = number of taxa. Equitability (E) was\nthe second community structure index determined; E measures the proportional abundances\namong the various taxa in a sample (Krebs 1978) and ranges from 0.00 to 1.00, with 1.00\nindicating all taxa in the sample are numerically equal. Equitability is expressed as:\nE = H/log2s","5\nwhere H = Shannon-Wiener function and S = number of taxa. Both H and E were calculated\nfor each sampling station.\nTotal benthic invertebrate densities, Corbicula fluminea, Corophium spp., and\nCeratopogonidae (Diptera) larval densities, H, and E were each compared between areas (i.e.,\nthe ferry channel and control area) and surveys using two-way analysis of variance (ANOVA)\n(Cruze and Hartzell 1991); invertebrate densities were tested for normality, and if necessary,\ntransformed (log10) prior to performing ANOVA. Normality was tested by calculating normal\nscores of the data, then conducting a correlation test between the normal scores and the data\n(Cruze and Hartzell 1991). Means from the three samples collected at each sampling station\nprovided the basic data entries for all statistical tests.\nSediments\nMedian grain size and percent volatile solids were each compared between areas (i.e.,\nthe ferry channel and control area) and surveys using two-way analysis of variance (Cruze\nand Hartzell 1991); median grain size and percent volatile solids were tested for normality\nand transformed (log10) prior to performing ANOVA. One low outlying value for median\ngrain size (Station W3, July 1994) was removed prior to using ANOVA. No statistical\ncomparisons for percent silt/clay were made because of the non-normal distribution of the\ndata and the lack of an adequate data transformation.\nRESULTS\nBenthic Invertebrates\nThe total numbers of taxa/categories collected in the ferry channel and control area\n(data combined for both areas) ranged from 11 in April 1994 to 27 in October 1994","6\n(Appendix Table 2). Mean numbers of taxa/categories (by survey) in the ferry channel and\ncontrol area were similar, ranging from 6 to 11 (Table 1).\nNo effect of the ferry channel dredging project on benthic invertebrate densities (total)\nwas detected in the statistical analysis, as indicated by the nonsignificant interaction\n(P = 0.08) between survey and area in the ANOVA (Table 2). However, benthic invertebrate\ndensities were significantly different between surveys (ANOVA, P = 0.00) and areas\n(ANOVA, P = 0.01). Benthic invertebrate densities were significantly higher (P < 0.05) in\nthe control area than in the ferry channel. In the control area, mean densities (by survey)\nranged from 2,307 organisms/m2 in July 1994 to 25,436 organisms/m² in April 1994\n(Table 3). Mean densities (by survey) in the ferry channel ranged from 2,017 organisms/m²\nin February 1994 to 23,954 organisms/m² in January 1995.\nDuring all eight surveys, Corbicula fluminea, Corophium spp., and Ceratopogonidae\nlarvae were generally the most common benthic invertebrates in both the ferry channel and\nthe control area. In both areas, Corophium spp. were generally the most abundant benthic\ninvertebrates (Fig. 2). We estimated that about 98% of the Corophium spp. were C. salmonis\nand the remainder C. spinicorne. Summaries by station for all eight benthic invertebrate\nsurveys are available upon request from NMFS, Northwest Fisheries Science Center, Point\nAdams Biological Field Station, P.O. Box 155, Hammond, Oregon 97121.\nNo effect of the ferry channel dredging project on Corbicula fluminea densities was\ndetected in the statistical analysis, as indicated by the nonsignificant interaction (P = 0.42)\nbetween survey and area in the ANOVA (Table 2). Corbicula fluminea densities were\nsignificantly different between surveys (ANOVA, P = 0.03) and areas (ANOVA, P = 0.00).\nCorbicula fluminea densities were significantly higher (P < 0.05) in the control area than in","7\nTable 1. Mean numbers of benthic invertebrate taxa/categories identified in samples collected\nduring eight surveys in Wahkiakum County Ferry Channel, Washington, and a\ncontrol area, 1993-1995. Each value for a station is the mean of three replicate\nsamples. The ferry channel was dredged after the January 1994 survey and prior to\nthe February 1994 survey.\nStation\nOct 94\nJan 95\nApr 95\nFeb 94\nApr 94\nJul 94\nOct 93\nJan 94\nFERRY CHANNEL\n11\n6\n6\n6\n8\n7\n5\n6\nW1\n7\n6\n9\n9\n6\n7\n6\nW2\n6\n7\n7\n8\n9\n7\n5\n7\n4\nW3\n5\n10\n9\n9\n5\n5\nW4\n7\n7\n4\n4\n7\n8\n13\n7\n5\n7\nW5\n6\n15\n16\n6\n7\n8\nW6\n5\n7\n14\n11\n8\n10\n16\n6\n7\nW7\n9\n--\n--\n11\n9\n7\n6\n8\n7\n6\n6\nMean\nCONTROL AREA\n9\n8\n7\n10\n13\n8\n8\nWC8\n10\n6\n9\n9\n6\n5\n6\n6\n8\nWC9\n8\n7\n6\n6\n9\nWC10\n6\n7\n10\n7\n8\n8\n11\n8\n9\nWC11\n7\n8\n10\n5\n8\n9\n7\n5\n5\nWC12\n6\n11\n8\n9\n11\n7\n10\nWC13\n9\n8\n10\n6\n8\n8\n5\n7\n5\nWC14\n6\n--\n--\n--\n7\n9\n8\n8\n7\n9\n7\n7\nMean","8\nTable 2. Results of two-way analysis of variance for selected benthic invertebrate parameters\nmeasured in Wahkiakum County Ferry Channel, Washington, and a control area,\n1993-1995. Results from eight surveys--October 1993, January, February, April,\nJuly, and October 1994, and January and April 1995--were used in the analyses. A\nsignificant difference (P 0.05) is indicated with an *.\nDegrees of\nP\nvalue\nfreedom\nF\nSource\nParameter\n5.40\n7\n0.000*\nBenthic invertebrate\nSurvey\n1\n6.23\n0.014*\ndensity (log 10),\nArea\n7\n1.90\n0.078\ntotal\nSurvey X area\n111\nTotal\n7\n2.39\n0.027*\nCorbicula fluminea\nSurvey\n1\n13.07\n0.000*\ndensity (log 1o)\nArea\n7\n1.03\n0.415\nSurvey X area\n111\nTotal\n0.000*\n7\n5.07\nCorophium spp. density\nSurvey\n1\n0.25\n0.615\n(log 1o)\nArea\n7\n1.53\n0.166\nSurvey X area\n111\nTotal\n7\n3.39\n0.003*\nCeratopogonidae larvae\nSurvey\n1\n22.12\n0.000*\ndensity\nArea\n7\n1.65\n0.129\nSurvey X area\n111\nTotal\n7\n11.76\n0.000*\nDiversity (H)\nSurvey\n0.156\n1\n2.04\nArea\n7\n1.00\n0.438\nSurvey X area\n111\nTotal\n7\n6.24\n0.000*\nEquitability (E)\nSurvey\n0.554\n1\n0.35\nArea\n7\n0.81\n0.579\nSurvey X area\n111\nTotal","9\nTable 3. Mean densities (number/m²) of benthic invertebrates collected during eight surveys\nin Wahkiakum County Ferry Channel, Washington, and a control area, 1993-1995.\nEach value for a station is the mean of three replicate samples. The ferry channel\nwas dredged after the January 1994 survey and prior to the February 1994 survey.\nStation\nJan 95\nApr 95\nJul 94\nOct 94\nOct 93\nJan 94\nFeb 94\nApr 94\nFERRY CHANNEL\n448\n4,789\n991\n14,971\n898\n11,571\n2,238\n1,491\nW1\n5,573\n4,952\n1,967\n1,772\n4,597\n2,229\n2,961\n5,227\nW2\n37,925\n9,043\n2,408\n1,803\n1,775\n17,447\n1,399\nW3\n3,995\n5,137\n1,281\n32,655\n2,319\n2,069\n3,297\n6,218\n19,818\nW4\n29,222\n3,628\n3,621\n2,226\n4,063\n1,639\nW5\n3,804\n9,926\n79,264\n10,142\n1,346\n23,618\n30,722\n1,639\n6,449\nW6\n7,910\n59,095\n7,752\n20,830\n42,130\n3,109\n6,582\nW7\n8,194\n3,192\n23,954\n13,914\n5,480\n2,430\n20,528\n5,046\n10,254\n2,017\nMean\nCONTROL AREA\n50,194\n3,896\n33,674\n3,495\n25,072\n66,399\n26,570\nWC8\n9,176\n1,991\n1,155\n39,648\n633\n3,875\n22,238\n3,745\n7,564\nWC9\n23,170\n15,171\n2,263\n5,983\n2,056\nWC10\n3,841\n14,693\n13,563\n37,233\n23,933\n3,850\n23,982\n17,036\n40,049\n51,799\nWC11\n6,128\n1,707\n21,868\n6,968\n5,397\n4,739\n1,899\nWC12\n4,023\n2,084\n28,305\n43,766\n57,215\n2,729\n11,201\n55,063\n40,101\nWC13\n6,916\n1,979\n963\n6,629\n5,063\n5,026\n2,405\nWC14\n3,822\n2,266\n21,653\n20,510\n11,362\n25,436\n2,307\n5,379\n23,586\n19,226\nMean","10\n30\n25\n20\n15\n10\n5\n0\nJan 95\nApr 95\nOct 93\nJan 94\nFeb 94\nApr 94\nJul 94\nOct 94\nFerry Channel\n30\n25\n20\n15\n10\n5\n0\nJul 94\nOct 94\nJan 95\nApr 95\nOct 93\nJan 94\nFeb 94\nApr 94\nControl Area\nMean number of Corophium spp./m² 2\nMean total number of organisms/m²\nFigure 2. Mean densities of benthic invertebrates (total) and Corophium spp. in Wahkiakum\nCounty Ferry Channel, Washington, and a control area, 1993-1995. The ferry channel\nwas dredged after the January 1994 survey and prior to the February 1994 survey.","11\nthe ferry channel. In the control area, mean densities (by survey) ranged from 636\norganisms/m2 in April 1995 to 2,783 organisms/m² in April 1994 (Table 4). Mean densities\n(by survey) in the ferry channel ranged from 196 organisms/m² in February 1994 to 1,370\norganisms/m² in October 1994.\nNo effect of the ferry channel dredging project on Corophium spp. densities was\ndetected in the statistical analysis, as indicated by the nonsignificant interaction (P = 0.17)\nbetween survey and area in the ANOVA (Table 2). Corophium spp. densities were\nsignificantly different between surveys (ANOVA, P = 0.00), but not between areas (ANOVA,\nP = 0.62). In the control area, mean densities (by survey) ranged from 545 organisms/m² in\nJuly 1994 to 20,022 organisms/m² in April 1994 (Table 5). Mean densities (by survey) in the\nferry channel ranged from 1,373 organisms/m² in February 1994 to 22,307 organisms/m² in\nJanuary 1995.\nNo effect of the ferry channel dredging project on densities of Ceratopogonidae larvae\nwas detected in the statistical analysis, as indicated by the nonsignificant interaction\n(P = 0.13) between survey and area in the ANOVA (Table 2). Densities of Ceratopogonidae\nlarvae were significantly different between surveys (ANOVA, P = 0.00) and areas (ANOVA,\nP = 0.00). Densities of Ceratopogonidae larvae were significantly higher (P < 0.05) in the\ncontrol area than in the ferry channel. In the control area, mean densities (by survey) ranged\nfrom 525 organisms/m² in July 1994 to 2,174 organisms/m² in October 1994 (Table 6). Mean\ndensities (by survey) in the ferry channel ranged from 399 organisms/m² in February 1994 to\n1,123 organisms/m² in January 1994.\nNo effect of the ferry channel dredging project on the benthic invertebrate community\nstructure, measured by H and E, was detected in the statistical analysis, as indicated by the","12\nTable 4. Mean densities (number/m²) of Corbicula fluminea collected during eight surveys in\nWahkiakum County Ferry Channel, Washington, and a control area, 1993-1995.\nEach value for a station is the mean of three replicate samples. The ferry channel\nwas dredged after the January 1994 survey and prior to the February 1994 survey.\nStation\nJul 94\nOct 94\nJan 95\nApr 95\nOct 93\nJan 94\nFeb 94\nApr 94\nFERRY CHANNEL\n25\n142\n284\n1,003\n139\n62\n994\nW1\n509\n278\n364\n534\n83\n99\n392\nW2\n466\n337\n1,223\n420\n198\n352\n976\n80\n337\nW3\n485\n164\n266\n1,701\n139\n256\n300\nW4\n645\n945\n1,822\n219\n238\n272\n219\nW5\n256\n235\n204\n1,476\n364\n296\n976\n639\n151\n482\nW6\n676\n1,201\n2,575\n1,358\n262\n497\n256\nW7\n559\n389\n646\n401\n448\n291\n1,370\n514\n395\n196\nMean\nCONTROL AREA\n2,285\n954\n3,137\n991\n4,153\n1,630\n4,742\n7,975\nWC8\n151\n318\n1,281\n62\n1,210\n1,179\nWC9\n670\n380\n1,547\n1,541\n151\n766\n420\n1,612\n843\nWC10\n945\n3,174\n2,331\n1,355\n1,899\n1,951\n6,147\n8,351\nWC11\n1,568\n56\n701\n179\n250\n262\n266\nWC12\n614\n111\n5,233\n713\n4,631\n698\n1,179\n5,391\n1,241\nWC13\n1,985\n93\n269\n287\n93\n86\n312\nWC14\n763\n31\n1,578\n1,795\n636\n2,783\n677\n1,168\n1,910\n2,476\nMean","13\nTable 5. Mean densities (number/m²) of Corophium spp. collected during eight surveys in\nWahkiakum County Ferry Channel, Washington, and a control area, 1993-1995.\nEach value for a station is the mean of three replicate samples. The ferry channel\nwas dredged after the January 1994 survey and prior to the February 1994 survey.\nStation\nJul 94\nOct 94\nJan 95\nApr 95\nOct 93\nJan 94\nFeb 94\nApr 94\nFERRY CHANNEL\n182\n13,103\n114\n4,313\nW1\n957\n275\n426\n9,228\n2,908\n1,257\n4,622\nW2\n1,226\n3,535\n1,139\n2,482\n1,013\n35,773\n6,428\n756\n1,683\n658\n670\n14,486\nW3\n2,664\n4,010\n1,287\n1,689\n494\n29,882\n1,090\nW4\n4,091\n17,860\n2,556\n834\n26,601\n1,998\n3,010\nW5\n2,180\n7,814\n1,010\n76,350\n8,666\n543\n19,240\nW6\n5,591\n28,987\n1,380\n5,326\n10,123\n39,564\n54,723\nW7\n6,842\n1,130\n2,689\n5,097\n6,317\n22,307\n12,253\n8,622\n1,373\n3,862\n1,436\n16,620\nMean\n3,364\nCONTROL AREA\n47,372\n2,473\nWC8\n6,619\n60,379\n17,697\n28,598\n1,124\n18,240\n114\n701\n17,996\n262\n34,473\n120\nWC9\n846\n5,600\n1,309\n537\n18,962\n11,732\n519\nWC10\n1,176\n12,220\n11,602\n849\n18,830\n32,170\n19,500\nWC11\n2,254\n13,368\n32,300\n40,632\n18,191\n5,659\n275\nWC12\n2,664\n343\n936\n1,207\n315\n21,117\n41,837\nWC13\n3,378\n47,567\n37,764\n49,823\n580\n8,580\n658\nWC14\n312\n213\n3,782\n590\n151\n3,424\n2,220\n20,022\n545\n17,243\n17,199\n9,339\nMean\n2,464\n19,956\n14,969","14\nTable 6. Mean densities (number/m²) of Ceratopogonidae larvae collected during eight\nsurveys in Wahkiakum County Ferry Channel, Washington, and a control area,\n1993-1995. Each value for a station is the mean of three replicate samples. The\nferry channel was dredged after the January 1994 survey and prior to the February\n1994 survey.\nStation\nOct 94\nJan 95\nApr 95\nApr 94\nJul 94\nOct 93\nJan 94\nFeb 94\nFERRY CHANNEL\n741\n238\n269\n1,155\n395\n710\n1,053\n371\nW1\n571\n145\n636\n1,439\n1,334\n488\n1,676\nW2\n1,220\n1,840\n614\n2,047\n333\n917\n645\n812\n509\nW3\n886\n932\n1,294\n404\n698\n803\n500\nW4\n1,389\n367\n426\n355\n1,402\n960\n1,152\nW5\n1,334\n1,812\n68\n9\n1,003\n482\n414\nW6\n1,621\n908\n74\n31\n46\n324\n102\n1,445\n68\n151\nW7\n500\n687\n749\n536\n399\n975\n463\n1,084\n1,123\nMean\nCONTROL AREA\n170\n704\n40\n562\n689\n642\nWC8\n417\n704\n312\n1,676\n2,661\n479\n3,628\n1,368\n1,834\nWC9\n2,096\n1,491\n423\n2,056\n1,655\n929\n2,637\nWC10\n1,599\n1,559\n2,634\n1,389\n1,182\n1,133\n519\nWC11\n2,013\n1,176\n874\n877\n2,637\n954\n1,062\n1,355\n4,007\n2,600\nWC12\n519\n204\n889\n1,454\n815\n636\n417\nWC13\n1,229\n1,309\n2,103\n1,118\n1,315\n318\n2,671\n1,769\n1,062\nWC14\n2,618\n2,174\n1,130\n986\n1,499\n1,320\n1,440\n1,667\n525\nMean","15\nnonsignificant interaction (P = 0.44 for H; P = 0.60 for E) between survey and area in the\nANOVA (Table 2). Both H and E were significantly different between surveys (ANOVA,\nP = 0.00), but not between areas (P = 0.16 for H; P = 0,55 for E). Mean H values (by\nsurvey) in the control area ranged from 1.02 in January 1994 to 2.22 in July 1994. In the\nferry channel, mean H values (by survey) ranged from 0.84 in April 1995 to 1.85 in July\n1994 (Table 7). Mean E values (by survey) in the control area ranged from 0.34 in October\n1994 to 0.70 in July 1994. In the ferry channel, mean E values (by survey) ranged from 0.30\nin October 1994 to 0,61 in July 1994 (Table 8).\nSediments\nAlthough median grain size was significantly smaller in the ferry channel than in the\ncontrol area (ANOVA, P = 0.00), no effect of the ferry channel dredging project on median\ngrain size was detected in the statistical analysis, as indicated by the nonsignificant interaction\n(P = 0.88) between survey and area in the ANOVA. The overall means for median grain\nsizes in the ferry channel and control area were 0.29 and 0.37 mm, respectively (Table 9).\nMedian grain size was not significantly different between surveys (ANOVA, P = 0.18). Mean\nmedian grain sizes in the ferry channel ranged from 0.24 mm in July 1994 to 0.32 mm in\nJanuary 1994, whereas in the control area, mean median grain sizes ranged from 0.33 mm in\nJanuary 1995 to 0.40 mm in October 1993 (Table 9).\nThe overall means for percent silt/clay in the ferry channel and control area were 2.8\nand 1.1%, respectively (Table 10). In the ferry channel, mean percent silt/clay ranged from\n0.1% in January 1994 to 8.6% in July 1994. Mean percent silt/clay in the control area ranged\nfrom 0.4% in October 1993 and January 1994 to 2.1% in April 1995.","16\nTable 7. Diversities (H) of benthic invertebrates collected during eight surveys in\nWahkiakum County Ferry Channel, Washington, and a control area, 1993-1995.\nThe ferry channel was dredged after the January 1994 survey and prior to the\nFebruary 1994 survey.\nStation\nJul 94.\nOct 94\nJan 95\nApr 95\nOct 93\nJan 94\nFeb 94\nApr 94\nFERRY CHANNEL\n1.82\n0.62\n2.07\n0.72\n1.24\n1.56\n1.01\nW1\n1.71\n1.00\n1.43\n1.30\n1.34\n1.39\n2.00\n1.59\n1.18\nW2\n0.41\n1.15\n1.48\n1.88\n0.86\n1.46\n1.32\nW3\n1.30\n0.93\n1.38\n1.38\n2.04\n0.55\n1.67\n1.33\n0.60\nW4\n0.58\n1.27\n0.83\n1.34\n1.91\nW5\n1.33\n0.90\n1.51\n1.94\n1.14\n0.29\n0.78\n0.39\n0.87\n0.95\nW6\n1.15\n0.56\n1.92\n0.43\n0.80\n1.25\n1.14\nW7\n0.97\n1.72\n1.03\n0.84\n1.26\n1.85\n1.03\n1.34\n1.07\n1.25\nMean\nCONTROL AREA\n0.37\n1.54\n0.87\n2.23\n1.27\n0.54\n1.13\nWC8\n1.32\n0.89\n1.97\n0.71\n2.02\n1.67\n0.95\nWC9\n1.60\n1.19\n1.84\n2.11\n0.98\n1.09\n1.39\nWC10\n1.75\n0.87\n0.89\n0.77\n1.02\n2.39\n1.09\n1.10\n0.93\n1.03\nWC11\n1.82\n0.86\n0.94\n1.52\n1.48\n1.57\n1.17\n1.68\n2.10\nWC12\n1.12\n0.36\n0.75\n0.42\n0.77\n2.52\n1.20\nWC13\n1.74\n1.52\n2.24\n1.41\n1.59\n1.02\n1.65\nWC14\n1.34\n1.12\n1.26\n2.22\n1.07\n1.13\n1.18\n1.58\n1.02\n1.03\nMean","17\nTable 8. Equitabilities (E) of benthic invertebrates collected during eight surveys in\nWahkiakum County Ferry Channel, Washington, and a control area, 1993-1995.\nThe ferry channel was dredged after the January 1994 survey and prior to the\nFebruary 1994 survey.\nStation\nOct 94\nJan 95\nApr 95\n94\nJul 94\nOct 93\nJan 94\nFeb 94\nApr\nFERRY CHANNEL\n0.21\n0.70\n0.24\n0.39\n0.69\n0.61\n0.53\n0.60\nW1\n0.50\n0.32\n0.63\n0.51\n0.46\n0.48\n0.54\nW2\n0.62\n0.41\n0.29\n0.13\n0.47\n0.74\n0.67\n0.46\n0.63\nW3\n0.53\n0.40\n0.59\n0.64\n0.17\n0.48\n0.22\n0.60\nW4\n0.42\n0.54\n0.48\n0.64\n0.16\n0.64\n0.47\n0.39\nW5\n0.29\n0.07\n0.30\n0.34\n0.65\nW6\n0.50\n0.14\n0.34\n0.11\n0.16\n0.34\n0.48\n0.66\n0.28\n0.42\nW7\n0.31\n0.32\n0.30\n0.38\n0.47\n0.50\n0.61\n0.49\n0.43\nMean\nCONTROL AREA\n0.51\n0.34\n0.12\n0.38\n0.31\n0.67\n0.40\n0.18\nWC8\n0.78\n0.34\n0.37\n0.62\n0.22\n0.40\n0.72\nWC9\n0.62\n0.54\n0.67\n0.33\n0.39\n0.27\n0.71\nWC10\n0.68\n0.31\n0.36\n0.27\n0.34\n0.34\n0.75\nWC11\n0.65\n0.37\n0.27\n0.28\n0.65\n0.66\n0.31\n0.57\n0.68\n0.50\n0.56\nWC12\n0.11\n0.35\n0.37\nWC13\n0.55\n0.25\n0.12\n0.27\n0.76\n0.48\n0.59\n0.71\n0.75\n0.47\n0.48\n0.36\nWC14\n0.52\n0.34\n0.38\n0.44\n0.57\n0.38\n0.37\n0.47\n0.70\nMean","Table 9. Median grain sizes (mm) of sediments sampled in Wahkiakum County Ferry Channel, Washington, and a control\narea, 1993-1995. The ferry channel was dredged after the January 1994 survey and prior to the February 1994\nApr 95\n0.35\n0.33\n0.45\n0.35\n0.21\n0.36\n0.30\n0.39\n0.39\n0.28\n0.31\n0.30\n0.31\n0.34\n0.29\n0.25\nJan 95\n0.27\n0.35\n0.31\n0.34\n0.35\n0.26\n0.43\n0.30\n0.33\n0.33\n0.31\n0.24\n0.32\n0.33\n0.16\n0.20\nOct 94\n0.38\n0.31\n0.29\n0.49\n0.37\n0.30\n0.35\n0.36\n0.29\n0.29\n0.29\n0.27\n0.29\n0.31\n0.21\n0.37\nJul 94\n0.40\n0.36\n0.34\n0.33\n0.39\n0.24\n0.66\n0.32\n0.30\n0.32\n0.28\n0.03\n0.28\n0.25\n0.31\n0.22\nFERRY CHANNEL\nCONTROL AREA\nApr 94\n0.38\n0.43\n0.33\n0.35\n0.38\n0.29\n0.37\n0.30\n0.48\n0.28\n0.32\n0.29\n0.32\n0.30\n0.28\n0.26\nFeb 94\n0.32\n0.35\n0.31\n0.51\n0.34\n0.39\n0.45\n0.37\n0.31\n0.35\n0.39\n0.29\n0.31\n0.34\n0.32\n0.24\nJan 94\n0.33\n0.40\n0.35\n0.37\n0.39\n0.42\n0.36\n0.36\n0.32\n0.30\n0.31\n0.31\n0.32\n0.36\n0.29\n0.32\nOct 93\n0.50\n0.37\n0.37\n0.47\n0.30\n0.45\n0.34\n0.40\n0.32\n0.31\n0.31\n0.32\n0.29\n0.30\n0.30\n0.31\nsurvey.\nStation\nMean\nWC8\nWC9\nWC10\nWC11\nWC12\nWC13\nWC14\nMean\nW1\nW2\nW3\nW4\nW5\nW6\nW7","Table 10. Percents silt/clay of sediments sampled in Wahkiakum County Ferry Channel, Washington, and a control area,\n1993-1995. The ferry channel was dredged after the January 1994 survey and prior to the February 1994\nApr 95\n2.6\n5.2\n0.5\n0.2\n0.7\n0.2\n7.8\n0.3\n2.1\n0.3\n0.3\n0.1\n0.3\n0.5\n0.8\n15.6\nJan 95\n5.0\n6.9\n0.2\n1.1\n1.0\n0.6\n0.5\n1.1\n1.6\n0.2\n1.0\n1.1\n0.2\n0.2\n19.8\n12.5\nOct 94\n0.8\n0.6\n2.7\n0.5\n0.7\n1.0\n0.2\n0.4\n0.2\n0.5\n1.7\n1.5\n1.3\n1.9\n10.6\n1.2\nJul 94\n0.3\n0.3\n8.6\n0.3\n0.0\n4.8\n0.4\n0.4\n0.9\n0.1\n0.2\n52.9\n0.3\n0.7\n0.1\n6.1\nFERRY CHANNEL\nCONTROL AREA\nApr 94\n0.3\n2.6\n0.6\n0.1\n0.3\n0.2\n1.5\n2.2\n6.8\n1.7\n1.1\n0.5\n0.8\n1.3\n0.2\n1.0\nFeb 94\n1.3\n0.6\n6.1\n1.1\n1.4\n0.7\n0.8\n1.0\n1.7\n0.7\n0.4\n0.5\n0.6\n1.0\n0.7\n5.1\nJan 94\n1.0\n0.1\n0.1\n0.3\n0.1\n1.1\n0.2\n0.4\n0.1\n0.1\n0.1\n0.0\n0.1\n0.4\n0.2\n0.1\nOct 93\n0.2\n0.2\n0.4\n0.7\n0.5\n0.1\n0.7\n0.4\n0.2\n0.1\n0.2\n0.1\n0.3\n0.4\n0.5\n0.3\nsurvey.\nStation\nMean\nWC8\nWC9\nWC10\nWC11\nWC12\nWC13\nWC14\nMean\nW1\nW2\nW3\nW4\nW5\nW6\nW7","20\nNo effect of the ferry channel dredging project on percent volatile solids was detected\nin the statistical analysis, as indicated by the nonsignificant interaction (P = 0.56) between\nsurvey and area in the ANOVA. Percent volatile solids were not significantly different\nbetween areas (ANOVA, P = 0.45), and overall, averaged 0,6% in each area (Table 11).\nPercent volatile solids were significantly different between surveys (ANOVA, P = 0.01). In\nthe ferry channel, mean percent volatile solids ranged from 0.5% in January 1994 to 0.8% in\nApril 1994 (Table 11). In the control area, mean percent volatile solids ranged from 0.5% in\nOctober 1994 and January 1995 to 0.8% in April 1994. Sediments from the ferry channel\nwere tested for contaminants prior to the dredging project and were found to be\nuncontaminated (Jon Gornick, COE, Portland District, P.O. Box 2946, Portland, Oregon\n97208. Pers. commun. 26 February 1996).\nDISCUSSION\nThe effects of dredging on benthic invertebrate communities vary widely. Morton\n(1977), who conducted a literature review of the ecological effects of dredging and dredge\nspoil disposal, noted that initial effects can range from negligible to severe and impacts range\nfrom short to long-term. Based on his literature review, Morton (1977) concluded that short-\nterm, small-scale dredging and dredge spoil disposal projects impacted benthic communities\nless than long-term, large-scale projects.\nWe were unable to detect any significant effect of the clamshell dredging project on\nthe standing crops of benthic invertebrates in Wahkiakum County Ferry Channel. Apparently,\nbenthic invertebrates in the dredged area were able to recolonize the area quite rapidly after\ndredging. In a study of the effects of dredging on benthic macroinvertebrates in a South","Table 11. Percents total volatile solids of sediments sampled in Wahkiakum County Ferry Channel, Washington, and a\ncontrol area, 1993-1995. The ferry channel was dredged after the January 1994 survey and prior to the\nApr 95\n0.5\n0.6\n0.4\n0.8\n0.6\n0.7\n1.2\n0.7\n0.7\n0.5\n0.8\n0.6\n0.5\n0.8\n0.9\n0.7\nJan 95\n0.4\n0.5\n0.7\n0.5\n0.5\n1.6\n0.9\n0.7\n0.6\n0.5\n0.6\n0.5\n0.3\n0.4\n0.5\n---\n0.5\nOct 94\n0.3\n0.5\n0.4\n0.6\n0.7\n0.9\n0.5\n0.6\n0.4\n0.4\n0.6\n0.5\n0.6\n0.6\n0.4\n0.5\nJul 94\n1.0\n0.6\n0.6\n0.6\n0.8\n0.7\n0.7\n0.7\n0.8\n0.5\n0.6\n0.6\n0.5\n0.6\n0.6\n0.6\nFERRY CHANNEL\nCONTROL AREA\nApr 94\n0.5\n0.6\n0.8\n1.0\n0.8\n0.7\n1.1\n0.8\n0.8\n0.6\n0.7\n1.0\n0.6\n1.1\n0.7\n---\n0.8\nFeb 94\n0.4\n0.5\n0.4\n0.5\n0.7\n0.5\n1.0\n0.6\n0.5\n0.4\n0.6\n0.6\n0.7\n1.1\n0.4\n---\n0.6\nJan 94\n0.4\n0.6\n0.6\n0.5\n0.4\n0.4\n0.7\n0.5\n0.8\n0.5\n0.6\n0.6\n0.4\n0.5\n0.7\n---\n0.6\nFebruary 1994 survey.\nOct 93\n0.6\n0.5\n0.6\n0.7\n0.6\n0.5\n0.8\n0.6\n0.8\n0.8\n0.8\n0.9\n0.3\n0.4\n0.5\n---\n0.6\nStation\nW1\nW2\nW3\nW4\nW5\nW6\nW7\nMean\nWC8\nWC9\nWC10\nWC11\nWC12\nWC13\nWC14\nMean","22\nCarolina estuary, Van Dolah et al. (1984) noted short-term effects of a dredging project, with\nsubstantial recovery within 3 months. They attributed much of the rapid recolonization to\nimmigration via sediments of the slumping channel walls, which were similar to the sediments\nremoved during dredging. Benthic invertebrates living in the slumping channel walls\nadjacent to Wahkiakum County Ferry Channel could have contributed to the rapid\nrecolonization of the dredged area by benthic invertebrates. Although the sediments outside\nof the ferry channel were not sampled, we assume that they were similar to those removed\nfrom the ferry channel. If the sediments in slumping channel walls had been considerably\ndifferent than those removed from the channel, then the benthos in the ferry channel may not\nhave recovered as rapidly.\nCorophium salmonis may also have migrated into the dredged channel from areas\nmore distant than the slumping channel walls. Davis (1978) observed that C. salmonis\nactively migrated into the water column in the Columbia River estuary. Corophium volutator,\na related Atlantic species, has been found to swim above the bottom during part of its life\n(Hughes 1988). If C. salmonis populations in the reach of the Columbia River near the\nWahkiakum County Ferry Channel exhibit similar behavior, they could have been carried into\nthe ferry channel by river currents. Muir (1990) found that Corophium salmonis was one of\nthe three most abundant organisms collected in the drift along the bottom of the river\ndownstream from Bonneville Dam.\nNo significant changes occurred in the benthic invertebrate community structure, as\nmeasured by H and E, in Wahkiakum County Ferry Channel as a result of the dredging\nproject. Ideally, all benthic organisms should have been identified to the same taxonomic\nlevel, preferably species, for the community structure assessments; however, this was not","23\npractical or feasible given the financial constraints of the study. Even though different\ntaxonomic levels of identification were used in calculating both H and E, we believe our\nstatistical comparisons are valid since similar taxonomic levels were used throughout the\nstudy. No attempt was made to compare our H and E values to those of other research\nstudies.\nOur study clearly demonstrates the need for at least one control area in environmental\nassessments of dredging projects. Also, it is important to conduct sampling prior to dredging\nin both the impacted and control areas. Underwood (1992) goes one step farther and states\nthe need for multiple control areas in environmental assessments, with sampling before and\nafter in both the impact and control areas. Unfortunately, it is not practical or economically\nfeasible to establish multiple control areas in most benthic invertebrate studies. Without the\ndata from the control area, we would not have been able to make accurate conclusions\nregarding the impact of the dredging project on the benthos in the ferry channel. Samples\ncollected in the control area provided a means of assessing natural variation in the standing\ncrops and community structure of benthic invertebrates in a specific reach of the lower\nColumbia River. Other researchers have noted that benthic invertebrate populations in other\nreaches of the lower Columbia River vary seasonally (Holton et al. 1984, McCabe and Hinton\n1993, Hinton et al. 1995). In Grays Bay (RM 23), Holton et al. (1984) observed that\nCorophium salmonis densities ranged from 4,122 organisms/m² in July 1981 to 31,754\norganisms/m² in February 1981. Hinton et al. (1995) noted significant (P < 0.05) temporal\ndifferences in standing crops of benthic invertebrates (total), including Corophium spp., in a\nstudy area between Miller Sands and Pillar Rock Island, Columbia River estuary (RM 26). In","24\nour study, densities of Corophium spp. fluctuated during the eight surveys, with the lowest\noverall density in July 1994.\nIn conclusion, we detected no significant effect (P > 0.05) of the ferry channel\ndredging project on benthic invertebrate densities or community structure from the statistical\nanalyses of the data. In addition, we detected no significant effect (P > 0.05) of the dredging\nproject on sediment median grain size or percent volatile solids.\nThis report does not constitute formal comments of the NMFS under the Fish and\nWildlife Coordination Act or the National Environmental Policy Act.","25\nACKNOWLEDGMENTS\nWe thank Lawrence Davis, Roy Pettit, Dennis Umphfres, Donald Gruber, and Nathan\nCook for their assistance in collecting benthic samples during this study. Benjamin Sandford\nprovided advice on the statistical analysis of the data. Finally, we appreciate the cooperation\nof the operators of the Wahkiakum County ferry during our sampling efforts.","26\nREFERENCES\nCruze, E., and B. Hartzell. 1991. Minitab reference manual, PC version, release 8. Quickset\nInc., Rosemont, PA.\nDavis, J. S. 1978. Diel activity of benthic crustaceans in the Columbia River estuary. M.S.\nThesis, Oregon State Univ., Corvallis, 170 p.\nHinton, S. A., G. T. McCabe, Jr., and R. L. Emmett. 1995. In-water restoration between\nMiller Sands and Pillar Rock Island, Columbia River: Environmental surveys,\n1992-93. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-NWFSC-23, 47 p.\nHolton, R. L., D. L. Higley, M. A. Brzezinski, K. K. Jones, and S. L. Wilson. 1984. Benthic\ninfauna of the Columbia River estuary. Final report on the benthic infauna work unit\nof the Columbia River Estuary Data Development Program, 179 p. plus appendices.\n(Available from CREST, 748 Commercial St., Astoria, OR 97103.)\nHughes, R. G. 1988. Dispersal by benthic invertebrates: the in situ swimming behaviour of\nthe amphipod Corophium volutator. J. Mar. Biol. Assoc. United Kingdom 68:565-579.\nKirn, R. A., R. D. Ledgerwood, and A. L. Jensen. 1986. Diet of subyearling chinook\nsalmon (Oncorhynchus tshawytscha) in the Columbia River estuary and changes\neffected by the 1980 eruption of Mount St. Helens. Northwest Sci. 60(3):191-196.","27\nKrebs, C. J. 1978. Ecology: the experimental analysis of distribution and abundance.\nHarper and Row. New York, 678 p.\nMcCabe, G. T., Jr., R. L. Emmett, W. D. Muir, and T. H. Blahm. 1986. Utilization of the\nColumbia River estuary by subyearling chinook salmon. Northwest Sci.\n60(2): 113-124.\nMcCabe, G. T., Jr., and S. A. Hinton. 1993. Benthic invertebrates and sediments in\nvegetated and nonvegetated habitats at three intertidal areas of the Columbia River\nestuary, 1992. Report to U.S. Army Corps of Engineers, Contract E9592012, 37 p.\n(Available from Northwest Fisheries Science Center, 2725 Montlake Blvd. E., Seattle,\nWA 98112.)\nMcCabe, G. T., Jr., W. D. Muir, R. L. Emmett, and J. T. Durkin. 1983. Interrelationships\nbetween juvenile salmonids and nonsalmonid fish in the Columbia River estuary.\nFish. Bull., U.S. 81(4):815-826.\nMorton, J. W. 1977. Ecological effects of dredging and dredge spoil disposal: a literature\nreview. U.S. Fish Wildl. Serv. Tech. Pap. 94, 33 p.\nMuir, W. D. 1990. Macroinvertebrate drift abundance below Bonneville Dam and its relation\nto juvenile salmonid food habits. M.S. Thesis, Portland State Univ., Portland, Oregon,\n40 p.","28\nMuir, W.D., and R. L. Emmett. 1988. Food habits of migrating salmonid smolts passing\nBonneville Dam in the Columbia River, 1984. Regul. Rivers: Res. and Manage.\n2:1-10.\nMuir, W. D., R. L. Emmett, and R. J. McConnell. 1988. Diet of juvenile and subadult white\nsturgeon in the lower Columbia River and its estuary. Calif. Fish and Game\n74(1):49-54.\nUnderwood, A. J. 1992. Beyond BACI: the detection of environmental impacts on\npopulations in the real, but variable, world. J. Exp. Mar. Biol. Ecol. 161:145-178.\nU.S. Army Corps of Engineers. 1992. Westport, Oregon-Puget Island, Washington,\nWahkiakum County Ferry Channel draft detailed project report, Section 107 study.\nU.S. Army Corps of Engineers, Portland District, P.O. Box 2946, Portland, Oregon,\n33 p. plus appendices.\nVan Dolah, R. F., D. R. Calder, and D. M. Knott. 1984. Effects of dredging and open-water\ndisposal on benthic macroinvertebrates in a South Carolina estuary. Estuaries\n7(1):28-37.","29\nAPPENDIX","30\nAppendix Table 1. Geographic locations of benthic sampling stations in Wahkiakum County\nFerry Channel, Washington, and control stations, 1993-1995. All stations\nbeginning with \"W\" were in the ferry channel; stations beginning with\n\"WC\" were in the control area. The depth (mean lower low water) is a\nmean from eight surveys.\nLatitude\nLongitude\nStation\nMean\ndepth (m)\n123°22.723\"W\n46°09.103\"N\n4.4\nW1\n123°22.708\"W\n46°09.081\"N\n4.0\nW2\n46°09.134\"N\n123°22.684\"W\n3.2\nW3\n46°09.132\"N\n123°22.672\"W\n3.0\nW4\n46°09.154\"N\n123°22.667\"W\nW5\n2.7\n123°22.638\"W\n46°09.147\"N\n2.5\nW6\n46°09.170\"N\n123°22.654\"W\n3.0\nW7\n46°08.825\"N\n123°20.311\"W\n1.3\nWC8\n123°20.265\"W\n46°08.800\"N\n4.0\nWC9\n123°20.110\"W\n2.6\n46°08.807\"N\nWC10\n46°08.833\"N\n123°20.000\"W\n1.9\nWC11\n123°19.999\"W\n46°08.820\"N\n4.0\nWC12\n46°08.830°N\n123°19.964\"W\n2.1\nWC13\n46°08.789\"N\n123°19.977\"W\n5.0\nWC14","31\nAppendix Table 2. Invertebrate taxa/categories found in Wahkiakum County Ferry Channel,\nWashington, and a control area, 1993-1995; the data were combined for\nboth areas for each survey.\n1995\n1994\n1993\nTaxon/category\nOct\nJan Apr\nOct\nJan\nFeb\nApr\nJul\nNemertea\nX\nX\nX\nX\nX\nX\nX\nNematomorpha\nX\nTurbellaria\nX\nX\nX\nX\nX\nX\nPolychaeta\nNeanthes limnicola\nX\nX\nX\nOligochaeta\nX\nX\nX\nX\nX\nGastropoda\nX\nLymnaeidae (unid. limpet)\nX\nFluminicola virens\nX\nX\nX\nJuga plicifera\nX\nX\nX\nBivalvia\nX\nCorbicula fluminea\nX\nX\nX\nX\nX\nX\nX\nAnodonta spp.\nX\nOstracoda\nX\nX\nX\nX\nAmphipoda\nCorophium spp.\nX\nX\nX\nX\nX\nCorophium salmonis\nX\nX\nX\nCorophium spinicorne\nX\nX\nX\nX\nX\nRamellogammarus spp.\nX\nRamellogammarus oregonensis\nX\nX\nX\nHyalella azteca\nX\nPontoporeia hoyi\nX\nIsopoda\nGnorimosphaeroma oregonensis\nX\nPorcellio scaber\nX","32\nAppendix Table 2. Continued.\n1995\n1994\n1993\nTaxon/category\nJul\nOct\nJan Apr\nOct\nJan\nFeb\nApr\nCopepoda\nHarpacticoida\nX\nHydracarina\nX\nX\nMiscellaneous Insecta\nCollembola adult\nX\nX\nX\nX\nPlecoptera nymph\nX\nEphemeroptera nymph\nX\nX\nX\nX\nX\nOdonata nymph\nX\nX\nX\nHemiptera\nX\nX\nTrichoptera larvae\nX\nX\nColeoptera larvae\nX\nMiscellaneous Diptera\nChironomidae larvae\nX\nX\nX\nX\nX\nX\nX\nX\nChironomidae pupae\nX\nX\nX\nX\nX\nX\nCeratopogonidae larvae\nX\nX\nX\nX\nX\nX\nX\nX\n11\n17\n27\n23\n15\nTotal no. of taxa/categories\n16\n14\n18"]}