John J. Goering

Large yearly production of phytoplankton in the Western bering strait.

Production in the western Bering Strait is estimated at 324 grams of carbon per square meter per year over 2.12x 104 square kilometers. An ice-reduced growing season makes this large amount of primary production unexpected, but it is consistent with the areas large upper trophic level stocks. The productivity is fueled by a cross-shelf flow of nutrient-rich water from the Bering Sea continental slope. This phytoplankton production system from June through September is analogous to a laboratory continuous culture.

The feeding, respiration and excretion of zooplankton in the Bering Sea during a spring bloom

The feeding, respiration, and excretion of Bering Sea net zooplankton were measured during the spring bloom. Respiration and excretion rates are related to body size by allometric equations with identical weight exponents, and ingestion rate is a function of body size and food concentration. Growth rates of the largeNeocalanus spp., estimated by assuming 70% of ingested food is assimilated and subtracting respiratory expenditures, agree reasonably well with population parameters from previous studies, but suggest that ingestion is slightly underestimated, respiration is slightly overestimated, or both. Rates of community grazing and excretion are calculated by applying the ingestion and excretion rates of individual organisms to the measured zooplankton populations. The community rates are compared to carbon fixation and nitrogen uptake rates by phytoplankton. Grazing by net zooplankton is equivalent to 18% of the daily phytoplankton production in the oceanic and outer-shelf regions, 25% in the mid-shelf region, and 6% in the coastal region. However, regional differences in the levels of primary productivity n result in about twice aa much phytoplankton remaining unaccounted for in the mid-shelf region as in the outer regions. Ammonium excretion by the net zooplankton community is equivalent to 13% of the daily ammonium uptake by phytoplankton in the outer-shelf region and in the mid-shelf and coastal regions values are 16 and 2%, respectively. These values overestimate the importance of zooplankton excretion because about half of the nitrogen uptake by phytoplankton was in the form of nitrate.

Patterns of nitrate utilization and new production over the Bering-Chukchi shelf

Abstract Time-integrated new production was calculated from estimates of nitrate consumption during summer over the Bering-Chukchi shelf. Time-zero or initial nitrate concentrations were estimated from a highly correlated end-of-winter nitrate-salinity regression. In the southeastern Bering Sea, new production was maximal over the 200 m isobath (70g C m −2 ) and minimal over the inner shelf ( −2 ) in Alaskan Coastal water. Downstream, in the northern Bering and southern Chukchi seas, no additional new production could be resolved in the Alaskan Coastal Water. Anadyr water, on the other hand, supported new production of up to 3.1 g C m −2 day −1 south of Bering Strait and 2.4 g C m −2 day −1 north of the strait. We estimate that over a 120 day growing season 288 g C m −2 year −1 was fixed as new production in this water mass resulting in the removal of 70–90% of the initial nitrate stock. Little additional new production in the Anadyr stream could be expected downstream in the western Chukchi Sea.

Near-surface silica dissolution in the upwelling region off northwest Africa

Abstract The rate of silica dissolution in the upper 25 to 60 m of the upwelling region off northwest Africa was determined by a stable isotope tracer technique capable of measuring dissolution in the presence of simultaneous silicic acid uptake. The dissolution rate increased with depth and surpassed the rate of silicic acid uptake between 5 and 30 m over the continental shelf. Silica dissolution in the upper 50 m was sufficient to supply all silicic acid taken up by the phytoplankton.

KINETICS OF SILICIC ACID UPTAKE AND RATES OF SILICA DISSOLUTION IN THE MARINE DIATOM THALASSIOSIRA PSEUDONANA1,2

Tracer techniques using the stable isotope 30Si were used to measure rates of silicic acid uptake and silica dissolution in silicon replete and silicon depleted populations of 2 clones of the marine diatom Thalassiosira pseudonana Hasle & Heimdal. Uptake kinetics were describable using the Michaelis‐Menten equation for enzyme kinetics, and no threshold concentration for uptake was evident. The maximum specific uptake rate of the estuarine clone 3H (0.062–0.092 · h−1) was higher than that of the Sargasso Sea clone 13‐1 (0.028–0.031 · h−1), but half‐saturation constants for uptake by the 2 clones were not measurably different (0.8–2.3 μM for 3H; 1.4–1.5 μM for 13‐1). There was little or no light dependence of uptake in populations grown under optimal light conditions prior to the experiment. Exponentially growing populations released silicic acid to the medium by dissolution of cellular silica at rates ranging from 6.5 to 15% of the maximum uptake rate.

Stable organic carbon isotopes in sediments of the north Bering-south Chukchi seas, Alaskan-Soviet Arctic Shelf

The δ13C and OC/N in carbonate-free sediments show an east to west cross-shelf trend within the north Bering-south Chukchi seas. Generally, the δ13C increases from the river deltas ( 10) through the adjacent sound (8–10) to the open shelf (<7). Sediment trap samples from southeast Chukchi Sea show complementary cross-shelf changes in δ13C and OC/N. These distributional patterns are similar to those generally observed in temperate shelves despite the peculiar environmental settings of the subarctic-arctic. The patterns of lateral changes in δ13C and OC/N in our study area are explained in the context of two-end member sources of organic carbon, terrigenous and marine. No significant correlations exist between sediment δ13C and OC/N and benthic biomass in the south Chukchi Sea. These suggest that the nature of organic carbon, as indicated by the δ13C and OC/N, is not the sole factor controlling benthic biomass in the above area. It is further suggested that the observed lateral changes in δ13C have a potential use as a proxy signal in the elucidation of the Quaternary transgressive-regressive history of Beringia.

Silicic acid uptake by natural populations of marine phytoplankton

Abstract The response of silicic acid uptake by phytoplankton populations to varyingsilicic acid concentrations has been investigated using a newly developed Si stable isotope tracer technique in the Peru upwelling region. Since silicic acid uptake follows the Michaelis-Menten expression for enzyme kinetics, a hyperbola describes the relationship between concentration and uptake. The half saturation constant ( K τ ) for uptake and the maximum uptake ( V max ) were 2·93 μg atoms Si. 1. −1 and 0·075 hr −1 , respectively. The uptake is light-dependent and this relation is also described by the Michaelis-Menten equation. Since uptake is both light- and silicic acid concentration-dependent, vertical profiles of it obtained with the Si isotope tracer technique can be interpreted from the interaction of light and silicic acid concentrations at different depths. The uptake of silicic acid by natural phytoplankton populations had diel periodicity, with a maximum about noon and significant nearly uniform rate at night. Nitrate reductase activity and 15 N-nitrate and 15 N-ammonium uptake had a similar diel periodicity.

Denitrification in the oxygen minimum layer of the eastern tropical Pacific Ocean

Abstract Molecular nitrogen and nitrite are produced concurrently from nitrate-15N added to the oxygen-deficient and nitrite-rich water below the thermocline in the tropical eastern Pacific Ocean. Molecular nitrogen originates by reduction of nitrate (denitrification) and not from the oxidation of ammonia by nitrate or nitrite. The ratio of molecular nitrogen produced to nitrate-nitrogen lost varied from 0·1 to 0·8. Denitrification decreased by 58% with an increase in oxygen saturation from 0·4 to 3·5%.

The production of biogenic silica and its accumulation on the southeastern Bering Sea shelf

Silicic acid uptake rates, biogenic silica concentrations, and210Pb sedimentation rates were measured on the southeastern Bering Sea shelf. These rates are used to describe the distribution of biogenic silica and approximate a steady-state budget for silica on the outer shelf of the Bering Sea. Specific uptake velocities (Vo) in the upper 10 m range from 0.002 to 0.015 h−1. No significant differences in specific uptake velocities were found between the coastal, middle, and outer domains. Average concentrations of biogenic silica were 299 and 429 mmol m−2 in the middle and coastal domains, respectively. The lower concentration in the outer shelf, 91 mmol m−2, was a result of greater grazing stress on diatom phytoplankton in that area. The estimated annual production of biogenic silica is 2.87 mol Si m−2 y−1 on the middle shelf and 1.64 mol Si m−2 y−1 on the outer shelf. The210Pb-derived sedimentation rate in the outer domain is 700 to 877 g m−2 y−1; 7 to 10% of the sediment is amorphous silica. Diffusive fluxes of silicic acid from the bottom, based on the gradients in interstitial silicic acid, are 114 to 276 mmol m−2 y−1 or 7 to 17% of outer shelf silica production. Assuming no advection of biogenic silica onto or from the outer domain, up to 65% of the biogenic production is incorporated into surface sediments and an estimated 18 to 35% dissolves in the water column.

The Effect of Salmon Carcasses on Alaskan Freshwaters

Many Alaskan freshwaters provide important spawning and nursery habitat for salmonid fishes. Pacific salmon are well known for their anadromous and semelparous natural history of rearing in the marine environment and returning to freshwater as adults to spawn once before dying in their natal habitat. Five species of anadromous Pacific salmon, Oncorhynchus nerka (sockeye or red salmon), O. kisutch (coho or silver salmon), O. gorbuscha (pink or humpback salmon), O. keta (chum or dog salmon), and O. tshawytscha (chinook or king salmon) spawn in Alaskan freshwaters. The time juvenile salmon reside in freshwater following emergence from the gravel as fry until smoltification (physiological preparation for migration to saltwater) depends on species and location. Because freshwater residence can range from virtually no time to several years, considerable variation in dependence on the freshwater habitat as a nursery environment exists. The sockeye salmon is the only Pacific salmon to have a juvenile stage that is usually dependent on a lacustrine habitat and a forage base of Zooplankton. Because lakes used for rearing by juvenile salmon are typically olig-otrophic, the productivity of sockeye lakes has been studied as a factor limiting sizes of salmon runs (see Chapter 8; and Burgner et al., 1969; Hyatt and Stockner, 1985; Stockner, 1981, 1987).