Environmental Drivers Overview

KRILL (EUPHAUSIIDS), SUCH AS EUPHAUSIA PACIFICA PICTURED ABOVE, ARE KEY PREY ANIMALS IN GULF OF ALASKA MARINE FOOD WEBS. ENVIRONMENTAL CONDITIONS DETERMINE THEIR ABUNDANCE AND DISTRIBUTION. (PHOTO CREDIT: RUSS HOPCROFT)

Do you see me here?
Hidden in plain sight, I’m
a humpback whale’s delight

 

Why are we monitoring Environmental Drivers?

A number of environmental factors drive marine ecosystems and thus affect the recovery of species and ecosystem services injured by the 1989 Exxon Valdez oil spill. These include currents, water temperature, salinity (salt content of the ocean tempered by fresh water from rivers and runoff from the land), concentrations of dissolved oxygen, nutrients, and chlorophyll; and the phytoplankton and zooplankton communities that are at the base of marine food webs. Water temperatures and salinities vary within the ocean water column as water masses become seasonally stratified or mixed by winds and currents.

We monitor environmental drivers in five, coordinated projects. Gulf Watch Alaska scientists collect oceanographic and plankton data: 1) along the Seward Line transect hat extends across the Gulf of Alaska shelf from a fixed Gulf of Alaska-1 (GAK-1) mooring on the continental shelf to the outer edge of the shelf, 2) along transect lines within Prince William Sound, 3) along transect lines within lower Cook Inlet and Kachemak Bay, and at point locations in Cordova and Seldovia Harbors and at GAK-1. GAK-1is positioned within the Alaska Coastal Current at the mouth of Resurrection Bay and has been recording data for more than 40 years. We also use vessels of opportunity to sample plankton with a Continuous Plankton Recorder along a transect across the Gulf of Alaska shelf and into Cook Inlet.

Our long-term monitoring and data collection across this large geographic area (provide important information on seasonal patterns and trends, as well as similarities and differences among locations within the Gulf of Alaska, and changing environmental conditions.

What are we finding?

The 2014 Gulf Watch Alaska Interim Synthesis Report and 2015 Annual reports documented the following trends in recent years:

  • A warm water anomaly (sometimes referred to as “the blob”) during the period 2014-early 2016. These unusual and persistent warm water conditions also interacted with warmer-than-average El Niño conditions during 2015-2016.

 

  • Shifts in phytoplankton and zooplankton abundance. These shifts may have important ramifications on species at higher levels in marine food webs, including humans.

 

  • Subtle differences in temperature and salinity at point (specific) locations. Consistent seasonal differences occurred at three locations in the study area that have also have biological implications. The nearshore waters in Seldovia Harbor in Kachemak Bay tend to be cooler than those in Cordova Harbor in Prince William Sound and at the Gulf of Alaska mooring (GAK-1) within the Alaska Current. Seldovia nearshore waters also have higher salinity than over the continental shelf at GAK-1.

AVERAGE MONTHLY TEMPERATURES AT LONG-TERM POINT LOCATIONS: SELDOVIA HARBOR, CORDOVA HARBOR, AND GULF OF ALASKA (GAK-1) MOORING.

AVERAGE MONTHLY SALINITY MEASUREMENTS AT LONG-TERM POINT LOCATIONS: SELDOVIA HARBOR AND GULF OF ALASKA (GAK-1) MOORING.