Project profile

Oceanographic Conditions in Prince William Sound

WHO WE AREPrincipal Investigators

Rob Campbell Prince William Sound Science Centerrcampbell@pwssc.org

www.gulfwatchalaska.orginfo@gulfwatchalaska.org

WHY ARE WE SAMPLING?Marine ecosystems are not static over time; they may change gradually from year to year or shift abruptly. Changes are in part driven by factors that oper-ate from the “bottom up,” such as environmental changes (e.g., changes in temperature, salinity, or turbidity) and biogeochemical dynamics that affect the availability and recycling of nutrients. Long term monitoring of the area affected by the Exxon Valdez oil spill is important, not only to assess the recov-ery of resources, but also to understand how the ecosystem is changing over time. This project provides physical and biological measurements that can be used to assess environmental conditions that have bottom-up influences on the marine ecosystems of Prince William Sound (PWS).

WHERE ARE WE SAMPLING?We deploy an autonomous moored profiler (AMP) in central PWS and conduct several regular vessel surveys within. Vessel surveys visit the mooring site, four historically sampled bays, and the major entrances (Hinchinbrook Entrance and Montague Strait) of PWS.

HOW ARE WE SAMPLING?We are using an Autonomous Moored Profiler (AMP, WetLabs, Inc.) to take con-tinuous envi ronmental measurements (see mooring diagram). This instrument, attached to a fixed mooring, measures temperature, salin-ity, oxygen concentration, chlorophyll-a concentra-tion, turbidity and nitrate concentrations as it ascends from its parking depth at 60 m to the surface every day. In addition, we conduct vessel surveys six times per year at sta tions throughout the PWS. At each station, we lower water bottles to collect water for nutrient and chlorophyll-a analysis, collect plankton, and complete a CTD (Conductivity-Temperature-Depth) cast to collect the same type of data with the same instrumentation as is col-lected by the instruments on the AMP.

Map of PWS showing stationary mooring site (black) and vessel-based sampling stations (red). The stationary mooring is located near Naked Island and vessel surveys are conducted within four bays and Hinchinbrook Entrance, Montague Strait, and central PWS(to collect ground-truth data and to service the mooring).

www.gulfwatchalaska.orginfo@gulfwatchalaska.org

WHAT ARE WE FINDING?In 2013, water temperatures at the surface were generally warmer than average during both summer and winter at most stations. Below the surface the picture was often the opposite, with temperatures cooler than average. The salinity of the surface water tended to be higher than average during winter and fresher than average (often by a considerable margin) during summer, particularly near the shore at the head of the bay. Similar to the pattern with temperature, the pattern of salinity in deeper water was just the opposite of that of the surface water. Future work will put these observations into the context of CTD data that has been collected for approximately 30 years.

The stationary environmental sampling instrument, an Autonomous Moored Profiler, is prepared for loading onto the research vessel to be deployed in PWS during the spring of 2013.

A state-of-the-art profiling

mooring was staged and

deployed in PWS in early

2013. The instruments on

the mooring collect data

on temperature, salinity,

chlorophyll fluorescence,

turbidity and nitrate con-

centration at a much higher

frequency (approximately

daily) than has ever been

done in the area before.

The AMP is attached to a cable anchored to the ocean floor. The instrument travels several times each day along the cable while taking and storing environmental measurements.

Gulf Watch scientist Rob Campbell prepares a CTD instrument for oceanographic sampling in PWS.

Zooplankton are captured in large, fine-mesh nets that are pulled vertically through the surface layer of the sound. The samples are returned to the lab for analysis of species composition and abundance.

The AMP system, prior to being moored in central PWS. The instrument moves vertically several times each day and collects continuous measures of the ocean environment.