Aquatic Ecology of the Elwha River Estuary Prior to Dam Removal 7 by Jeffrey J

Chapter Aquatic Ecology of the Elwha River Estuary Prior to Dam Removal 7 By Jeffrey J. Duda, Matthew M. Beirne, Kimberly Larsen, Dwight Barry, Karl Stenberg, and Michael L. McHenry Abstract The removal of two long-standing dams on describing the fish assemblage of the the Elwha River in Washington State will estuary and migratory patterns of juvenile initiate a suite of biological and physical salmon; (3) descriptions of the aquatic changes to the estuary at the river mouth. and terrestrial invertebrate communities Estuaries represent a transition between in the estuary, which represent an freshwater and saltwater, have unique important food source for juvenile assemblages of plants and animals, and fish and are important water quality are a critical habitat for some salmon indicators; and (4) the diet and growth species as they migrate to the ocean. This patterns of juvenile Chinook salmon chapter summarizes a number of studies in the lower Elwha River and estuary. in the Elwha River estuary, and focuses These data represent baseline conditions on physical and biological aspects of the of the ecosystem after nearly a century ecosystem that are expected to change of changes due to the dams and will be following dam removal. Included are data useful in monitoring the changes to the sets that summarize (1) water chemistry river and estuary following dam removal. samples collected over a 16 month period; (2) beach seining activities targeted toward Chapter 7 176 Coastal Habitats of the Elwha River, Washington—Biological and Physical Patterns and Processes Prior to Dam Removal Introduction of freshwater and marine drivers migration to the marine environment important for ecological processes. also was estimated. We studied fish As juvenile salmon migrate from This affects the amount, complexity, distribution, abundance, and migration freshwater rearing areas, they undergo biological productivity, and physical timing for all salmonids using the Elwha the physiological, behavioral, and conditions of estuarine habitats, which River estuary and examined the diet life history changes necessary for varies among river systems. Although and growth rates of juvenile Chinook transition to life in the ocean. Estuaries the role of estuaries has been deemed salmon. The aquatic and terrestrial are recognized as an important part of important for some Puget Sound macroinvertebrate communities of this migration (Simenstad and others, Chinook populations (Simenstad and the estuary also were surveyed. These 1982; Bottom and others, 2005b). others, 1982; Beamer and Larsen, animals play a central role as prey for Some salmon species, such as Chinook 2004), the significance of the Elwha salmon and are indicators of water (Oncorhynchus tshawytscha) and chum River estuary and nearshore (coastal quality that should be responsive to (O. keta) can spend extended periods marine water zone extending from high physical changes associated with (weeks to months) in the estuarine tide elevation to the limit of the photic dam removal. Other studies are environment, whereas others such as zone) to Chinook salmon populations being conducted on fish ecology by pink salmon (O. gorbuscha) largely is relatively unknown. We set out to colleagues elsewhere in the watershed forego extended use of estuarine areas describe the existing conditions of some (for examples, see Burke and others, in favor of ocean rearing (Groot and key ecological components of the lower 2008; Connolly and Brenkman, 2008; Margolis, 1991). It is hypothesized that Elwha River and its estuary prior to dam McHenry and Pess, 2008; Pess and salmon use estuarine habitats because removal. others, 2008, Brenkman and others, they provide a higher growth potential, Research efforts focused on 2008a, b; Duda and others, in press), facilitate the physiological transition collecting physical (water chemistry; in the nearshore proximal to the Elwha to saltwater conditions, and reduce see also Magirl and others, 2011, River, and in the Strait of Juan de Fuca the risk of predation (Quinn, 2005). chapter 3, this report, for salinity (for example, Shaffer and others, 2009). All of these factors may play a role in and temperature data) and biological Juvenile Chinook salmon samples higher growth and survival during the data from throughout the estuary and from these studies were obtained to subsequent marine life history phase adjacent riverine and nearshore areas assist in estimating several life history (Ruggerone and others, 2009). Estuarine in the Elwha River study area (fig. 7.1) traits, including age and growth (otolith fish assemblages fluctuate seasonally, prior to dam removal. Water samples microstructure), feeding (stomach based on migration timing, habitat were collected monthly to measure contents), and genetics (fin clips). This structure and connectivity, and physical nutrient concentrations from stations information should help provide a better factors such as salinity and temperature. dispersed in the lower river (2 sites), in understanding of Chinook salmon life Estuaries vary in size (see Duda and the estuary (4 sites), and in the nearshore histories and help inform adaptive others, 2011, figs. 1.8–1.10, chapter 1, (1 site). Seasonal use of the estuary management of the population following this report) and in the relative influence and nearshore by salmon during their dam removal and recolonization of the Elwha River watershed. Aquatic Ecology of the Elwha River Estuary Prior to DamIntroduction Removal 177 IEC Bosco Creek ES1 ES2 WESC Dudley Pond Figure location WASHINGTON STATE EXPLANATION Uppermost saltwater influence Outmigrant screw trap Water nutrient sampling site Lower Elwha Klallam Tribe Reservation Boundary Hunt Road Channel West-side Dike Figure 7.1. Sampling locations where water nutrients, benthic and terrestrial insects, and fish samples were collected in the Elwha River, Washington, study area. watac11-0558_fig7-01 Chapter 7 178 Coastal Habitats of the Elwha River, Washington—Biological and Physical Patterns and Processes Prior to Dam Removal Water Nutrients Water Sample Chemistry Laboratory, Seattle, Wash. Collection and Laboratory This procedure and laboratory were the same that were used by Morley and Inorganic nutrients are important Analysis of Nutrient constituents for cell growth and often others (2008) and Duda and others (in limit population growth and drive Concentrations press) for samples collected throughout competitive interactions; therefore, the Elwha River watershed. Water samples were collected Total nitrogen and total they play a central role in determining monthly from seven locations in the presence and abundance patterns of biota. phosphorous were analyzed using lower Elwha River and estuary (fig. 7.1). the persulfate digestion method of The availability of essential nutrients in Sites included one main stem (Lower the water column can limit the amount Valderrama (1981). The procedure Elwha River – main stem) and one side of Armstrong and others (1967) was of biological productivity and thus channel (Lower Elwha River – side modified for the analysis of NO3 and the character of the entire ecosystem. channel) location in the lower Elwha Measurement of nutrients through time NO2. Water samples were passed River; the groundwater fed outflow of through a cadmium (Cd) column where also can reflect patterns in seasonal the tribal hatchery (Bosco Creek) that the nitrate (NO3) was reduced to nitrite biological productivity, as nutrients serves as a primary source of surface are diminished during periods of high (NO2). This NO2 was then diazotized water to the east estuary; the tidally with sulfanilamide and coupled with growth (for example of algae and other influenced lentic sloughs east of the primary producers during the summer N-(1-naphthyl)-ethylenediamine to river mouth in the east estuary (ES1 and form an azo dye. The sample was then growing season) and are higher during ES2); the disconnected lake to the west periods of biological dormancy. The passed through a 15 mm flowcell and of the river mouth (Dudley Pond); and absorbance measured at 540 nm. The availability of nutrients in any watershed the surf zone (Nearshore – Strait of Juan depends on both biological and physical procedure is the same for the NO2 de Fuca) 25 m east of the river mouth analysis less the Cd column. Nitrate properties. Natural forces such as rainfall, in the Strait of Juan de Fuca. Samples concentration equals the (NO3 + geology, atmospheric deposition, and were collected across a range of tidal sedimentation drive levels of available NO2) concentration minus the NO2 conditions at approximately 30-day concentration. A modification of the nutrients, which are then consumed intervals, with interruptions in sample by autotrophic organisms and further Slawyk and MacIsaac (1972) procedure collection at all sites in November 2006 was used for the analysis of ammonium modified by allochthonous energy inputs (inclement weather) and July 2007 from the surrounding landscape. Other (NH4). Water samples were treated with (processing error). phenol and alkaline hypochlorite in the factors largely caused by human activity, Water samples were collected for presence of ammonia (NH3) to form such as resource extraction, fertilization, analysis of total nitrogen (TN), total and industrial pollution also can affect the idophenol blue (Berthelot reaction). phosphorous (TP), dissolved inorganic Sodium nitroferricyanide was used as nutrient levels in a watershed. - nitrogen (nitrate [NO3 ], ammonia

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