Maximum Primary Production Research Articles

Recent shallow marine Ostracoda of the Ikerssuak (Bredefjord) District, Southwest Greenland

Abstract. From a study of 15 grab samples collected from the littoral and sublittoral of the Ikerssuak (Bredefjord) district, SW Greenland, one myodocopid and 18 podocopid ostracod species were recovered. These constitute an indigenous fauna and the majority have been recorded from Greenland before. Leptocythere castanea and Leptocythere lacertosa are new to Greenland, and have not previously been confirmed from the western Atlantic. Copulating pairs of Hemicythere borealis were found in an intertidal embayment near the town of Narssaq. This species reproduced just before the late summer-autumn maximum of primary production in the area, and at the warmest time of the year. Semicytherura nigrescens, which has been recorded previously in SW Greenland, may have a similar distribution pattern to certain Subarctic Mollusca in western Greenland.

Effects of light fluctuations on the growth and productivity of Antarctic diatoms in culture

This work shows that the low division rates observed in diatoms in Antarctic waters seem to be due to conditions of irradiance rather than to the low temperature: low light intensity and light fluctuations are two factors which depress the division rate of diatoms. However, with regard to the productivity, Antarctic diatoms seem well-adapted to their turbulent environment. Cells grown in alternating periods of light and dark, notably a 2:2 regime which simulates conditions of vertical mixing, reach a higher rate of productivity than algae grown in continuous light. This difference may be due to the better use of light energy observed in the former group. In the Antarctic Ocean, which is characterized by frequent mixing of water masses, this increased efficiency of light utilization could be a way of adaptation, allowing the algae to overcome the restraints imposed by low light and low temperature, and to reach a higher productivity than expected. The low values of Ik and Imax as well as the absence of detectable photoinhibition indicate that Antarctic diatoms are capable to sustain their maximum primary production rate over a wide range or irradiance levels. On the other hand, the highest productivity in 2:2 regime shows that these species are more efficient when grown under fluctuating light. These results lead us to assume that the Antarctic species are well-adapted to live in the extreme conditions of light encountered in Antarctic Ocean: low irradiance and alternance of low and high light intensities.

Vertical distributions of primary production and grazing by Calanus glacialis jaschnov and C. hyperboreus kr�yer in Arctic waters (Barents Sea)

Simultaneous measurements of phytoplankton primary production, and zooplankton grazing by Calanus glacialis and C. hyperboreus were carried out over a 24h period at two stations northeast of Spitzbergen in July and August 1985. Phytoplankton biomass was concentrated in a sub-surface maximum, and our results suggested that 65% to 90% of the carbon produced was grazed by these copepods. At both stations maximum grazing rates by these zooplankton were observed within and below the depth of maximum primary production. At least one third of regenerated primary production could be sustained by ammonia excreted by the large zooplankton species Calanus glacialis and C. hyperboreus.

Vertical relationships between chlorophyll, production and copepods in the eastern tropical Pacific

Data consisting of high resolution profiles of in situ chlorophyll, copepods and primary production have been measured with a towed Batfish and profiling pumping system at two sites named ‘BIOSTAT’ (9°45'N, 93°45'W) and ‘DOME’ (7°19'N, 83°25'W) sites during March 1981. Primary production profiles were generated from Batfish profiles using a chlorophyll/light model and incubated pump samples, the latter with high vertical resolution of 3–5 m. The BIOSTAT site had a subsurface chlorophyll maximum situated at ˜50 m, and a production maximum at a depth of 40 m Copepods had a mean depth centroid corresponding to the production maximum although their distribution was more uniformly dispersed from 0 to 40 m. The latter observation indicated that copepods occurred at depths of high production potential and low biomass rather than high total production and high biomass as found at 40 m depth. The DOME site had a mixed surface layer of chlorophyll (0–20 m) while copepods were located at the base of the chlorophyll layer and primary production maximum located at the surface (0–10 m). The areal daily production measured at the BIOSTAT and DOME sites were 0.27 and 0.80 mg C m −2 day −1 respectively.

Surface temperature and transport in Lake Tahoe: inferences from satellite (AVHRR) imagery

Analysis of satellite infra-red images in summer at Lake Tahoe, California-Nevada, shows that upwelling on the west side of the lake causes an east-west temperature gradient that changes in strength from early spring to late summer, with maximum horizontal gradients in late June and early July. The mean temperature fields, sequences of individual images, and empirical orthogonal function analysis all suggest the presence of a large anticyclonic gyre in the north of the lake and a weaker cyclonic gyre in the south. This agrees with a numerical model of the lake's surface circulation, which has been driven by the measured diurnal summer wind fields. This circulation pattern is different from that reported at other lakes and may be an important factor in maintaining areas of maximum primary productivity seen in past synoptic studies of the lake.

Ammonium and phosphorus flux through the microplankton community in Agulhas Bank waters

The size-related activities of important heterotrophs and autotrophs were compared at the surface and at the subsurface chlorophyll maximum (Chlmax) in Agulhas Bank waters. The netplankton fraction was dominated by Nitzschia spp. and ciliates, small (diameter c. 3μm) microflagellates being the most abundant nanoplankton group. Uptake ratios of ammonium to phosphate for the total microplankton community were different at the two depths. With reference to the Redfield ratio, it appears that at least 48 per cent of the nitrogen ration at the Chlmax was regenerated even though nitrate was in ample supply. These assimilation ratios also suggest a very large contribution from recycled nitrogen other than ammonium in surface waters. It is unlikely that phosphorus would ever become limiting, except perhaps at the primary production maximum. Microplankton uptake and regeneration of both ammonium and phosphorus were approximately in balance, indicating that variations in assimilation ratios were the result of heter...

Influence of the biological and physical environment on the vertical distribution of mesozooplankton and micronekton in the eastern tropical Pacific

The day/night vertical distributions of mesozooplankton and micronekton biomass and that of a large number of copepod species to a depth of 1 000 m are described and contrasted in detail from two eastern tropical Pacific stations, the DOME station, in a region of continuous upwelling and the BIOSTAT station, in a non-upwelling area. The effects of various biological parameters such as the zones of primary production and chlorophyll maxima plus physical parameters, such as temperature, salinity and oxygen concentrations, on the distributions of the species and mesozooplankton and micronekton biomass are examined. The thermocline depth appeared to have the greatest influence of all the physical factors on the vertical distribution of the copepod species. The vertical distribution of many species was truncated in the region of the oxygen minimum layer with very few species found below this layer. The vertical distribution of copepod molts in the top 1 000 m showed that the molts probably originated at the depths at which they were found and that the molts from the euphotic zone did not reach the deep water. Copepod species association at different depths showed that few species had common depth distributions during both day and night. The highest degree of association occurred at night in the region of the thermocline. At depths below the thermocline, the degree of similarity in vertical distributions was greatly reduced. The biomass of mesozooplankton at these two stations is compared to other regions of the tropical oceans described in the literature and shown to be among the highest values recorded. The oxygen minimum layer and the thermocline had the greatest impact on species vertical distribution. The biomass of mesoplankton was about twice as high and the number of copepods between three and four times as high at the DOME site as compared to the BIOSTAT site, and evidence suggested that this was influenced by the higher primary production in this region. The difference in micronekton biomass between sites was less, with DOME having about 1.2 to 2.2 the biomass. This suggests that the influence of the higher level of primary productivity at the DOME was evidence of the higher trophic levels.

Fundy Tidal Power Development and Potential Fish Production in the Gulf of Maine

The possible effects of tidal amplitudes altered by Fundy tidal power development upon potential fish production in the Gulf of Maine are examined with a marine ecosystem model. Three areas off the Maine coast are delineated on the basis of winds, tides, and the extent of vertical mixing. An optimum kinetic energy from wind and tide exists for maximum primary production in the water column. Primary production in the model is the base for a simple pelagic food chain leading from phytoplankton through zooplankton to fish. If the construction of a tidal power dam in the upper Bay of Fundy results in a 5–10% increase in tidal amplitude, our first-order model predicts that enhanced vertical mixing from May to October will increase potential fish production along the Maine west coast by 7–12%. Fish production along the Maine east coast and in offshore waters is predicted to remain at present levels. Climatic variation is predicted to have as large an impact on fish production as man-induced changes in vertical mixing caused by tidal power development.

Population dynamics and production of cladoceran zooplankton in the highly eutrophic Lake Kasumigaura

The growth rate, birth rate, death rate and production of the cladocera of Lake Kasumigaura were studied. Standing crop of zooplankton seemed to be governed by predation rather than food. Maximum productivity of cladocerans was observed in late August and early September. There were differences in production between sampling stations. The highest production was recorded in the most eutrophic basin, where heavy water blooms of Microcystis aeruginosa occurred. Maximum secondary production coincided with maximum primary production, which was mainly due to M. aeruginosa. Cladocerans probably utilize decomposed or decomposing Microcystis cells and bacteria in summer. Estimates of annual production of cladocerans varied from 4.2 to 13.1 g dry wt · m−3, and annual P:B ratios ranged from 36 to 108. The production of cladocerans in Takahamairi Bay was 2.7% of gross primary production.

Standing stock, vertical distribution and flux of planktonic foraminifera in the Panama Basin

The relationships between planktonic foraminifera in the upper 2000 m of the water column and those in sediment traps and deep-sea sediments of the Panama Basin were investigated as part of the Composition, Flux and Transfer Experiments (CFATE) and the Sediment Trap Intercomparison Experiment (STIE) July–Dec. 1979. Planktonic foraminifera larger than 333 μm, sampled during the July–August trap deployment cruise, occurred most abundantly in the euphotic zone with maximal populations associated with the chlorophyll and primary production maxima both located in the upper thermocline just below the mixed layer. Juvenile abundances exceeded those of the >333 μm adults by 3–4 orders of magnitude and their depth distribution systematics indicated that most foraminifera reproduction occurs prior to sinking of the adults from the euphotic zone. Macroscopic aggregates and fecal pellets were identified as major carriers of smaller sized shells from the euphotic zone. During the July–August cruise, the species changed from an assemblage dominated by G. theyeri to one dominated by G. ruber; the live G. theyeri population sank passively from the euphotic zone in early August with a mean settling speed of 150 m day −1 while the G. ruber population grew in. The abundance of empty shells of all species in the upper 200 m varied by a factor of 40 during the deployment cruise and peaked on July 30, 1979. This variability was reflected in foraminifera collection rates of sediment traps deployed at 305 m for 24- and 6-h periods. The trap and watercolumn data were combined to calculate mean sinking speeds (>333 μm fraction) of several dominant foraminiferal species ( G. ruber and G. theyeri, 500 m day −1; G. dutertrei, 2000 m day −1). Size and weight analysis of empty shells from plankton tows yielded values of empty shell density (calculated on a spherical basis using maximum shell dimension) ranging from 0.12 and 0.15 g cm −3 ( G. theyeri and G. ruber) to 0.60 g cm −3 ( G. dutertrei). These speeds and shell densities were found to be consistent with the laboratory sinking experiments of Berger and Piper (1972) and Fok-Pun and Komar (1983). It was concluded that shell fluxes through the water column may be calculated with reasonable accuracy using a modified version of the Bishop et al. (1977) settling model and empty shell size distribution data from pump and plankton tow collections. The Fok-Pun and Komar (1983) settling model is recommended for future modelling efforts but requires a more extensive set of measurements of each foraminiferal specimen to be made. The interpretation of foraminiferal flux profiles, based on the collections of sediment traps, plankton tows, and pumps deployed on time scales shorter than several days, must take into account the very short residence times of empty shells in the water column and short term temporal variability in empty shell production rates. Populations of >333 μm foraminifera sampled in Nov.–Dec. 1979 were reduced by a factor of six relative to the July–Aug. values. The cruise-to-cruise differences were due to reduced primary production and greater mixed layer depth. Planktonic foraminifera were well preserved in sediment traps deployed for 112 days at 665, 935 and 1770 m, although aragonitic pteropod shells were partially dissolved. The fluxes of many species into the 935 m trap could not be explained based on the standing stock data from the July–August cruise alone and it was noted that species fluxes during STIE were comparable to or exceeded maximal values measured by Thunell and Reynolds (1984) in bi-monthly time series traps deployed at the same location during the whole of 1980. The moored trap data could only be explained by higher mean foraminifera shell fluxes in the interval between trap deployment and recovery, consistent with the Bishop and Marra (1984) model of primary production and carbon flux at the STIE site. Primary differences between core top samples and trap samples, were explained by the loss from the sediments of dissolution prone species, G. theyeri and G. ruber leaving an assemblage dominated by the dissolution resistant species, G. dutertrei.

Primary and Bacterial Production in Two Dimictic Indiana Lakes

The relationship between primary and bacterial production in two dimictic Indiana lakes with different primary productivities was examined during the summer stratification period in 1982. Primary production rates were calculated from rates of HCO(3) incorporation by natural samples, and bacterial production was calculated from rates of [H-methyl]thymidine incorporation by natural samples. Both vertical and seasonal distributions of bacterial production in the more productive lake (Little Crooked Lake) were strongly influenced by primary production. A lag of about 2 weeks between a burst in primary production and the subsequent response in bacterial production was observed. The vertical distribution of bacterial production in the water column of the less productive lake (Crooked Lake) was determined by the vertical distribution of primary production, but no clear relationship between seasonal maxima of primary and bacterial production in this lake was observed. High rates of bacterial production in Crooked Lake during May indicate the importance of allochthonous carbon washed in by spring rains. Bacterial production accounted for 30.6 and 31.8% of total (primary plus bacterial) production in Crooked Lake and Little Crooked Lake, respectively, from April through October. High rates of bacterial production during late September and October were observed in both lakes. Calculation of the fraction of bacterial production supported by phytoplankton excretion implies an important role for other mechanisms of supplying carbon, such as phytoplankton autolysis. Several factors affecting the calculation of bacterial production from the thymidine incorporation rates in these lakes were examined.

Utilization of Phytoplankton by Zooplankton during the Spring Bloom in a Nova Scotia Inlet

Coulter counter and microscope counts were used to estimate filtration and ingestion rates experimentally for total zooplankton caught by a 233-μm mesh net from two depths during the spring bloom in Bedford Basin. Initially, most phytoplankton were <20 μm with larger, chain-forming diatoms becoming more important as the bloom developed. Peak concentrations were >14 μg chlorophyll∙L−1and >1 mg C∙L−1and particle volume was >10 mm3∙L−1. Maximum primary production was >30 mg C∙m−3∙h−1. Dominant phytoplankton included Chaetoceros septentrionale early in the bloom, followed by Skeletonema costatum and Thalassiosira, Rhizosolenia, and Chaetoceros spp. Barnacle nauplii and Acartia hudsonica were the most common zooplankton near surface and Pseudocalanus sp. in deeper water. Ingestion was usually greatest at or near peaks in the Coulter counter particle spectrum. Filtration rate was proportional to grazer size and amount ingested and also to ambient particle concentration for near-surface but not deeper zooplankton. Higher ingestion was measured with the Coulter counter but microscopic counts gave higher filtration rates. Smaller surface-layer zooplankton apparently destroyed cells or chains that were not completely ingested. Microscopic estimates of particle volume ingested were 9–60% of that measured with the Coulter counter, suggesting utilization of detritus. Despite discrepancies in what the methods apparently measured, neither suggested a saturating functional response at ambient concentration, but with further concentration, both methods showed reduced filtration activity. Neither method revealed evidence for size-selective feeding, even when particles were compared on the basis of their maximum dimensions, but optical counts showed that single cells or chains of cylindrical shape were preferred to needle-like or spiney cells. Selection for biomass peaks could not be demonstrated using cell volume calculated from microscopic measurement. The 233-μm zooplankton utilized about 10–30% of daily primary production during the bloom.

The Epontic Algal Community of the Ice Edge Zone and Its Significance to the Davis Strait Ecosystem

The ice algae community in the dynamic outer edge zone of the Davis Strait pack ice was investigated in April-May 1978. Surveys of the epontic community were made using a remote camera system, a fibrescope, an ice corer, and in situ C14 incubation chambers. The undersurfaces of the floes were generally flat, containing slight undulations and small depressions of up to 10 cm. In the bottom few centimetres a transition was noted from hard ice to more fragile, but still firm, crystalline ice. Epontic flora was highly patchy and almost entirely restricted to the bottom few centimetres of the floes. Average concentrations in the bottom 6 cm of ice was 10.24 mg chl a/cu m. The pack ice bloom occurred in April and May with a peak occurring in May. The maximum primary production rates of 2.4 mg C/sq m/d occurred at a light intensity of 1.8 mu epsilon/sq m/s. Photosynthesis appeared to be inhibited at light levels above 20 mu epsilon/sq m/s. The dominant genera of the epontic flora were Navicula , Nitzschia , and Pleurosigma ; species composition of the epontic algal community differed significantly from that of the plankton. Two other ice algae communities were noted; a sandwich community in the middle of an ice floe, dominated by Asteromphalus hookeri and Thalassiosira gravida ; and a floe surface community which was on one occasion observed being seeded from the plankton. The total contribution of the epontic algae to the primary production of the Davis Strait was estimated to be approximately 7x10**7g C/y, or less than 1% that of the phytoplankton. The contribution may still be important, however, as it precedes the phytoplankton bloom and is the only algal concentration under heavy pack ice. Key words: Davis Strait, pack ice, epontic, primary production, ice algae

Benthic nutrient flux in a shallow coastal environment.

Ammonia and nitrate efflux from a fine sand in Carmarthen Bay was studied by incubating undisturbed cores of sediment on board ship. At the end of each incubation, the macrofaunal and bacterial biomass in each core and the organic content of the sediment were determined. Oxygen consumption was measured in another series of cores. The relationship between ammonia flux and biomass was investigated using a lattice of hypotheses approach to multiple linear regression, where all possible submodels of a general model are fitted. Ammonia flux was significantly related to the biomass of polychaetes and molluscs and "other macrofauna" but the inclusion of bacterial biomass did not improve the regressions. The estimated annual efflux of ammonia was 778 mmol N m-2 which is 44% of the estimated annual nitrogen demand of the phytoplankton. However, at the time of maximum primary production in June, only 16% of the phytoplankton requirement for nitrogen was met by benthic ammonia flux. Nitrate efflux was an order of magnitude less than that of ammonia and reached a maximum in the autumn. No significant relationship was found between oxygen consumption and macrofaunal or bacterial biomass at any time of the year.

Uptake of nitrogenous nutrients by phytoplankton in a barrier Island estuary: Great South Bay, New York

The uptake of urea, nitrate and ammonium by phytoplankton was measured using 15N isotopes over a one-year period in Great South Bay, a shallow coastal lagoon. The bay is a unique environment for the study of nutrient uptake since ambient concentrations of NO 3 − NH 4 + and urea remain relatively high through the year, and phytoplankton are probably never nutrient limited. Urea nitrogen averaged 52% of the total assimilated, while ammonium represented 33% and nitrate 13%. High rates of ammonium uptake occurred only at low urea concentrations (ca< 1-μg-atom urea l −1). Over the sampling period urea was present in relatively high concentrations, averaging 5·35 μg-atom N l −1, while means for ammonium and nitrate averaged 1·94 and 0·65 μg-atom N l −1, respectively. Total N uptake measured with 15N averaged about 3·3 times the calculated (from elemental ratios and 14C productivity measurements) N needs of the phytoplankton population. Highest nitrogen uptake occurred in the summer and coincided with the primary production maximum.

The streamside effect in a Carex lyngbyeiestuarine marsh: The possible role of recoverable underground reserves

In a comparison of streamside and back marsh stands of Carex lyngbyei in an Oregon estuarine marsh, the maximum biomass and net annual aerial primary productivity of the streamside stands were 50% higher. Aerial productivity rates on a unit of biomass basis were similar except during the late winter-early spring period and in the fall. Studies of recoverable underground photosynthate reserves coupled with the net aerial primary productivity measurements indicate the timing of growth and the mobilization of reserves were important factors in the streamside effect (greater biomass and net annual aerial primary productivity).

Repartition spatio-temporelle, biomasse et production des populations zooplanctoniques du lac d'aydat en periode estivale

Lake Aydat is a young eutrophic lake (mean depth 7.4 m, area 6o ha) situated in the french Central Massif. Secondary production was studied during the summer months June and July. In early summer, dissolved oxygen in the deep layers gradually gets depleted, and depletion reaches the 7m level in July. Zooplankton is therefore concentrated in the upper layers: Rotatoria are very abundant and the various species are segregated in space and / or succeed each other in time, thus maximally exploiting the water layers favorable to their development. Cladocera are represented by small species, which sharply increase in numbers at the time of maximum primary production, and cause a dramatic drop in primary production. They are in competition with the Rotatoria. Copepods are the least abundant group, but they were in a reproductive phase at the time of this study.

Seasonal Distribution, Abundance, and Growth of Larval Capelin (Mallotus villosus) in the St. Lawrence Estuary and Northwestern Gulf of St. Lawrence

Capelin (Mallotus villosus) larvae in the St. Lawrence estuary and northwestern Gulf of St. Lawrence were most abundant in 1974 and 1975 in the upper estuary in early June; this coincided with the spring peak in primary production. A spectacular decline (&gt;99%) in larval abundance between June and September resulted principally from their downstream transport by currents. In October and November larval capelin were concentrated in a large counterclockwise gyre located in the northwestern Gulf between Anticosti Island and Pointe des Monts. This region is within the area of maximum primary production in the estuary and Gulf and may serve as an important feeding area for larval capelin. Length of capelin larvae at the end of the first growing season in the estuary and northwestern Gulf was greater than that of capelin from Newfoundland, Labrador, and Greenland. However, this difference may have resulted from sampling biases. Daily growth rates of capelin larvae from these areas were similar. Key words: capelin, Mallotus villosus, St. Lawrence, seasonal distributions, larval transport, growth, vertical distribution

Surface Circulation Pattern in the Gulf of St. Lawrence

Using all available oceanographic data in the Gulf of St. Lawrence between 1950 and 1969, a network of average stations was formed for the months of June, July, August, November, and for the winter period. The dynamic method was applied to calculate the geostrophic circulation in the Gulf during these months based on a variable reference layer.The main features of the reference layer are the steep slope along the Gaspé coast and the existence of three depressions in the Laurentian Channel, southeast and west of Anticosti Island, and in the central region of Cabot Strait. Its depth varies from 10 to 50 m in the Magdalen Shallows to more than 300 m in part of the Laurentian Channel. The general two-way flow in all entrances to the Gulf, the existence of a permanent anticlockwise gyre west of Anticosti Island, and the Gaspé and Cape Breton currents with which are associated the highest velocities in the Gulf are the main features of the circulation pattern. The circulation patterns obtained agree with the results of synoptic observations.Cyclonic and anticyclonic gyres are common in the Gulf. A comparison of the circulation patterns obtained in this study and the results of the International Biological Programme Study of the Gulf reveal that such cyclonic and anticyclonic gyres are responsible, at least in part, for the areas of maximum primary productivity west and northeast of Anticosti Island, and for the so-called "desert areas" in the northeastern side of the Gulf.

Ecology of Zooplankton of the Cape Thompson Area Alaska

In a survey of the physicochemical characteristics, primary productivity and occurrence of zooplankton in fresh and brackish waters of Cape Thompson, Alaska, between June 28, 1960 and August 7, 1961, 14 species of Cladocera and 38 species of Copepoda (13 Calanoida, 11 Cyclopoida and 14 Harpacticoida) were distinguished in collections from 10 lakes, 8 lagoons and 111 pools. Seventy—three percent of all species were monocyclic; 13 per cent dicyclic; 9 per cent tricyclic; and 4 per cent tetracyclic. The maximum of primary production was correlated with maximal numbers of zooplankton, maximal number of eggs per ovigerous female in the Cladocera, and maximal occurrence of copepodids. Many Copedoda produced eggs in late fall and early winter when primary production was low. Autumnal production of eggs by these species may be possible because of storage of energy as lipids during the period of high environmental energy, and use of the stored energy at the end of the developmental period to form eggs. Analysis of community structure among zooplankton showed: 10 species with affinities and 7 interrelated recurrent groups occurred in the lakes; 3 species with affinities and 1 recurrent group occurred in the lagoons; 4 species with affinities and 3 interrelated recurrent groups occurred in the coastal pools; and no species with affinities occurred in the inland pools. One cladoceran, one cyclopoid and one or two calanoid copepods of different genera formed the major recurrent groups. The relationships between recurrent groups were the result of species within those related groups having similar distribution and overlapping developmental cycles. Closely allied species occupied different aquatic habitats, but when congeneric species co—occurred, there were differences in size and life cycles.