Sea ice algae, a major food source for herbivorous plankton and benthos in the eastern Bering Sea.

Rolf Gradinger, Bodil Bluhm. Katrin Iken (UAF)

Hypotheses

(H1) Sea ice algal communities are the main sources of algal biomass and primary productivity in the BEST study area in spring during periods of ice cover.

(H2) The accumulation of ice algal biomass is following the seasonal and regional gradients in light and nutrient availability.

(H3) Release of ice-derived particulate organic material (POM) occurs mainly during periods of ice melt.

(H4) The carbon stable isotope ratio (13C) of sea ice POM differs from pelagic material.

(H5) The 13C ratio can be used to trace the sea ice-derived material through the Bering Sea food web.

Bering Sea ice

Resting place for mammals

and birds

Primary Production

by ice algae

Seed for spring

phytoplankton blooms

Spring food pulse to

pelagic and benthic

herbivores

Water column

processes (light,

mixing, stratification)

Bering Sea ice

Resting place for mammals

and birds

Primary Production

by ice algae

Seed for spring

phytoplankton blooms

Spring food pulse to

pelagic and benthic

herbivores

Water column

processes (light,

mixing, stratification)

Objectives(1) measure chemical (nutrients, salinity) and physical parameters (ice thickness, snow depth, ice temperature, light) of sea ice and the under-ice water layer; (2) describe and quantify the temporal and spatial variability of ice algal parameters (algal pigments, taxonomic composition, size spectra, POC, PON, 13C ratio)(3) quantify the primary production of ice algae (using labeled precursors);(4) quantify the same parameters as in objectives (1) and (2) for the phytoplankton immediately under the sea ice; and quantify algal pigments and 13C stable isotope ratio in benthic sediments;(5) determine characteristics of sedimenting particles (species/particle type, algal pigments, PON, POC, 13C and 15N) by deploying drifting short term (<24hours) sediment traps under Bering Sea ice

Approach- 3 expeditions, four participants, 15 stations each- 3 ice floes per station, one with sediment traps (>12 hours)- Zodiak and/or from ice breaker- plankton nets, water column (CTD), van Veen grabs

BEST study area and prospective sampling grid. For each process station (green boxes on map), we will ideally sample several ice floes (I), as well as water column (P) and benthos (B) to obtain biological and physical data.

+ planktonic and benthic isotope samples

Field data: biological and physical parameters

Biological:Biomass (I,P)Abundance (I,P)Size spectrum (I,P)Prim. Production (I,P)POC / PON / Chl a (I,P,B)Isotope ratios (I,P,B)Physical:Ice thickness (I)Snow cover (I)Temperature (I,P)Salinity (I,P)Light (I,P)Nutrients (I,P)

Turnover ratesExperiments during expedition/in Fairbanks (climate control rooms)

one pelagic (copepod), one benthic species (amphipod)

Outreach- a project-specific web page up be end of 2007- Bering Sea school district: village of Golovin - Martin L. Olson School in Golovin- field class with students in 2009- Nome in fall 2007?- Fairbanks High School Science Seminar series in 2008- host a Teacher-at-sea in 2009?- interest from German TV team to participate in expedition in 2008(two people, 2 weeks)- Sea ice class (March 2008) in Barrow, Alaska (anyone interested?)