Ocean Indicators Methods and Background Materials

Hydrography, Zooplankton, and Ichthyoplankton Sampling

The Newport Hydrographic Line

Most of the biophysical indicators we use to characterize the oceanic habitat for juvenile salmon come from sampling along the Newport Hydrographic Line (Figure HZI-01). We sample the coastal waters off Newport at biweekly intervals year-round, weather permitting. Continuous sampling began in May 1996, but historical data exists for the same stations from sampling in 1973 (Peterson and Miller 1975), 1983 (Miller et al. 1985), and summer 1990-1992 (Fessenden 1995).
 

Figure HZI-01. Map of the Newport Hydrographic Line, a transect of established stations used in oceanographic sampling by Northwest Fisheries Science Center and Oregon State University research teams since the mid 1970s. The seven regularly sampled stations fall between 1-25 nautical miles from the Oregon coast. Data collected from station NH-5, located 5 nautical miles off Newport Oregon, are used to develop ocean ecosystem indicators, and are presented in the stoplight chart for adult salmon survival. Map courtesy of David Reinert (OSU). Credit: NOAA Fisheries

Cruises were conducted during daylight hours from May 1996 to September 2001 as our 37-ft research vessel, R/V Sacajawea, was unsafe to run at night. However, with the acquisition of a larger, 54-ft research vessel, R/V Elakha, we could begin sampling at night in September 2000, capturing daily migrating zooplankton such as krill.

During our biweekly sampling, we conduct a CTD cast (Conductivity, Temperature, and Depth; Seabird SBE19) at each station, and we measure the surface water transparency with a Secchi disc. Since 2005, the CTD casts have included fluorometry (WetLabs fluorometer) and oxygen (Seabird oxygen) sensors. 

We collect a surface water sample for chlorophyll-a, nutrients, and phytoplankton at each station. The nutrients are analyzed using a Technicon Autoanalyzer. Chlorophyll-a is extracted from glass–fiber filters in 90% acetone and then analyzed using a Turner Designs Fluorometer. Phytoplankton are enumerated by species using an inverted microscope, counting a minimum of 500 cells and reporting as cells per liter. 

At each station, we also collect a vertical plankton net (diameter: 0.5-m; mesh: 202-µm) fitted with a flowmeter from near the seafloor to the surface (or from 100 m maximum depth to the surface in deeper waters). We also tow a double oblique bongo net (diameter: 0.6-m; mesh: 335-µm) over the upper 20 meters of the water column for macrozooplankton such as ichthyoplankton, euphausiids, pteropods, and decapod larave. The vertical nets are towed during daylight hours, and the bongo nets are towed during the night (at least one hour past sunset), except for NH-1, which is too shallow to tow the bongos at night.  

Zooplankton are subsampled using a Stempel pipette, identified and enumerated to species and life history stage using a dissecting scope, and reported as individuals per m³. Biomass is estimated by multiplying the number of individuals per m³ by the taxa's dry weight (using sourced values or our lab's measurements). Carbon content is calculated assuming carbon is 40% of dry weight. 

Northern California Current Broadscale Ecosystem Survey

From 1998 to 2003, five transects from Newport, Oregon (Newport Hydrographic Line) to Crescent City, California, were sampled five times per year as part of the U.S. Global Ocean Ecosystem Dynamics (GLOBEC) program. After the GLOBEC project ended, we continued to sample the same transects as time and funding allowed. The broad-scale sampling has evolved into a semiannual Northern California Current Ecosystem Survey, which includes the expansion of the Newport Hydrographic Line out to 200 miles offshore and new transects as far north as La Push, Washington. The same sampling methods as the Newport Hydrographic Line are used on the NCC broad-scale surveys, with the addition of multiple water depths being sampled using a 12-bottle Niskin rosette. Additionally, the Juvenile Salmon and Ocean Ecosystem Survey samples north of the Newport Hydrographic Line at least three times per year. As a result, the Newport biweekly data are nested within multiple broad-scale surveys allowing for greater interpretation of the locally derived data.

Juvenile Salmon Sampling Program

Since 1998, juvenile salmon have been sampled at multiple stations from Newport, OR to Father and Son, WA (Figure JSS-01). We collect pelagic fish from the upper 20 m of the water column using a 264 rope trawl (NET Systems, Inc.; 30 × 20 × 100 m). Fifty individuals are randomly selected for identification and measurement from each trawl sample. We also measure and freeze up to 60 juvenile salmon of each species and size class (i.e., subyearling or yearling Chinook, based on size) for further examination in the lab. 

At each station, we also collect:

• Sea surface temperature and salinity
• Depth profiles of salinity, temperature, oxygen, chl fluorescence (Seabird SBE–19 or SBE-25 CTD)
• Water transparency (Secchi disk and/or a transmissometer)
• Oblique Bongo net tows using a 0.6 m diameter net fitted with 335-µm mesh

Acknowledgments

Many individuals have contributed to the dedicated hard work collecting the data presented on these pages. We are indebted to the many scientists and ship's crew who participated in the ocean sampling programs. Special thanks to JoAnne Butzerin for the initial design and editing of these pages, and Jo Ann Akada for IT support. 

Funding for data collection and data analysis came from the U.S. GLOBEC program NOAA–Center for Sponsored Coastal Ocean Research; grants NA 67RJ0151 and NA 86OP0589, from the NOAA Fisheries and the Environment (FATE) Program, NOAA-SAIP, NOAA-BiOp, and NOAA Cooperative Research Program. Grants from the National Ocean Partnership Program (NA97FE0193), the National Science Foundation (9907854–OCE), the Bonneville Power Administration, and US Marine Biodiversity Observation Network support this work. 

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