Process-Oriented Studies
The goal of any process study is the development of strong, testable hypotheses
and the design of field/laboratory experiments to repudiate these hypotheses.
The results of these studies should be used to augment or modify retrospective
and monitoring studies, but they also will provide needed input, particularly
biological rates, for modeling studies. The development and use of appropriate
new technologies (rapid discrete and continuous sampling, and non-invasive
techniques such as optical counters, acoustics, and remote sensing) is strongly
encouraged and should be incorporated into any field sampling program.
Moreover, U.S. GLOBEC encourages coordination with other U.S. and international
research programs presently conducting process studies in the Bering Sea to
further our advancement of knowledge and avoid duplication of effort.
Process studies should be focused on the key species and factors which lead to
the production and control of these species. Process studies will ideally be
conducted over several years to examine interannual variability and will include
both a Eulerian-frame (fixed grid or moorings) and a Lagrangian-frame (tracking
a patch or water parcel) approach.
Field studies will be conducted to examine the processes at the critical periods
when they most influence zooplankton production and should occur at the
appropriate temporal and spatial scales to elucidate the controlling mechanisms.
Process studies fall into two broad space/time categories: small- and
meso-scale. Meso-scale (10-100 km) processes include distribution and movements
of plankton in relation to features that are stable (fronts) or predictable
(eddies, ice extent, "cold pool") from year to year. Variability in large-scale
physical forcing may be expected to affect the location and/or intensity of
these features in different climatic regimes.
Meso-scale process studies will entail physical measurements from satellites,
shore- or ship-based observations, and drifter/mooring-based sensors. Biological
observations would involved repeated at-sea sampling or enumeration of
zooplankton and their food or predators. Emphasis should be placed at "pulse
points" that could be expected to vary the most interannually or in some way
reflect the status of the Bering Sea ecosystem.
Small-scale studies (1 m-10 km) will examine elements that affect individual
survival including diel vertical migrations, predator-prey interactions, growth,
and mortality. These studies should utilize repeated sampling at one location
or tracking a population for a period of time to allow continuous or repeat
sampling. Some behavioral and physiological components may require controlled
experiments using either ships, floating mesocosms, or shore laboratories.
Six cruises are recommended:
- An early spring cruise (March-April). Process-oriented studies conducted
during this cruise will examine meso-scale physical and biological conditions
leading to the initiation of the spring bloom, and will provide an estimate of
the timing and magnitude of the spring bloom. Vital rates of key primary and
secondary producers will be monitored. Moorings and drifters will be deployed.
- A mid- to late-spring cruise (May). Process-oriented studies will be
devoted to studies of small-scale patchiness of zooplankton in relation to
physical conditions, food concentrations and predator distributions throughout
the diel cycle. Zooplankton collections will be taken during this cruise to
examine growth and egg production rates for comparison to available
laboratory-derived rates. Comparative samples will be collected inside and
outside of the cold pool. Zooplankton food dependencies and feeding rates will
also be determined.
- A broad-scale cruise, conducted in the summer (June-July). This cruise
will examine the abundance and distribution patterns of zooplankton in relation
to predators and prey. Vertical and horizontal distributions of zooplankton and
their predators and prey will be collected. Concurrent measurements of physical
conditions will occur using ADCP and CTD casts. In some years cooperation with
NMFS may augment this research effort.
- A cruise dedicated to the main run of Bristol Bay sockeye salmon (end of
June). Process-oriented work will focus on the food habits and growth samples
of returning salmon in relation to prey availability.
- Summer predator surveys (June-August). Meso-scale studies of prey
selectivity and diel consumption rates of important predators will be examined
to estimate predation mortality of the key species. Fine scale studies of the
mechanisms attracting or concentrating zooplankton in some areas (fronts,
eddies, vertical stratification) will be examined. The impact of large
concentrations of predators (schools, flocks) on depleting food resources will
be addressed. Regions near the Pribilof Islands are recommended as survey sites
to facilitate studies of sea birds and marine mammal food habits. Surveys near
Unimak Pass and the outer 200 km shelf/slope are recommended to examine salmon
feeding behavior. Secondary study sites could be determined by coordination
with the broad-scale cruise.
- Fall cruise to retrieve moorings and conduct hydrographic surveys.
