Phytoplankton Primary Production Rates Research Articles

Assessing Pigment-Based Phytoplankton Community Distributions in the Red Sea

Pigment-based phytoplankton community composition and primary production were investigated for the first time in the Red Sea in February-April 2015 to demonstrate how the strong south to north environmental gradients determine phytoplankton community structure in Red Sea offshore regions (along the central axis). Taxonomic pigments were used as size group markers of pico, nano- and microphytoplankton. Phytoplankton primary production rates associated with the three phytoplankton groups (pico-, nano- and microphytoplankton) were estimated using a bio-optical model. Pico- (Synechococcus and Prochlorococcus sp) and Nanophytoplankton (Prymnesiophytes and Pelagophytes) were the dominant size groups and contributed to 49% and 38%, respectively, of the phytoplankton biomass. Microphytoplankton (diatoms) contributed to 13% of the phytoplankton biomass within the productive layer (1.5 Zeu). Sub-basin and mesoscale structures (cyclonic eddy and mixing) were exceptions to this general trend. In the southern Red Sea, diatoms and picophytoplankton contributed to 27% and 31% of the phytoplankton biomass, respectively. This result induced higher primary production rates (430 ± 50 mgC m-2 d-1) in this region (opposed to CRS and NRS). The cyclonic eddy contained the highest microphytoplankton proportion (45% of TChla) and the lowest picophytoplankton contribution (17% of TChla) while adjacent areas were dominated by pico- and nanophytoplankton. We estimated that the cyclonic eddy is an area of enhanced primary production, which is up to twice those of the central part of the basin. During the mixing of the water column in the extreme north of the basin, we observed the highest TChla integrated (40 mg m-2) and total primary production rate (640 mgC m-2 d-1) associated with the highest nanophytoplankton contribution (57% of TChla). Microphytoplankton were a major contributor to total primary production (54%) in the cyclonic eddy. The contribution of picophytoplankton (Synechococcus and Prochlorococcus sp) reached maximum values (49%) in the central Red Sea. Nanophytoplankton seem to provide a ubiquitous substantial contribution (30-56%). Our results contribute to providing new insights on the spatial distribution and structure of phytoplankton groups. An understanding and quantification of the carbon cycle in the Red Sea was made based on estimates of primary production associated with pico-, nano- and microphytoplankton.

Long-term variations in primary production in a eutrophic sub-estuary. I. Seasonal and spatial patterns

Daily rates of phytoplankton primary production were calculated from measurements of light saturation curves of photosynthesis for 20 yr at 6 stations on the Rhode River, Maryland (USA). Daily production, corrected for the geometry and spectrum of the underwater light field, av- eraged 1319 (range 1.4 to 15 800) mg C m −2 d −1 . Log-transformation of the exact solution for depth- integrated daily production permitted linear analysis of seasonal and spatial patterns in production and the factors that determine it. The seasonal signal was the greatest source of variation, followed by spatial then interannual. The seasonal pattern was driven by coinciding summer maxima in both the chlorophyll a (chl a) biomass, B, and the light saturated photosynthetic rate normalized to chl a, P B max. The spatial pattern was characterized by a region in which production was relatively constant despite declining depth, a station at which production was reduced by truncation of the depth profile of production, and an area where mean production was lowest but variance was highest, due to local flow causing either localized blooms or washout of biomass and high turbidity at the station furthest up the estuary. Analysis of the components contributing to the variance in production indicated that variance in B and P B max added nearly equally to it. Covariance between B and the light attenuation coefficient reduced the variance in production. The analytical approach adopted here allowed these patterns to be discerned against a high degree of overall variability, and should be similarly useful in a wide range of systems.

The role of ocean acidification in systemic carbonate mineral suppression in the Bering Sea

Ocean acidification driven by absorption of anthropogenic carbon dioxide (CO2) from the atmosphere is now recognized as a systemic, global process that could threaten diverse marine ecosystems and a number of commercially important species. The change in calcium carbonate (CaCO3) mineral saturation states (?) brought on by the reduction of seawater pH is most pronounced in high latitude regions where unique biogeochemical processes create an environment more susceptible to the suppression of ? values for aragonite and calcite, which are critical to shell building organisms. New observations from the eastern Bering Sea shelf show that remineralization of organic matter exported from surface waters rapidly increases bottom water CO2 concentrations over the shelf in summer and fall, suppressing ? values. The removal of CO2 from surface waters by high rates of phytoplankton primary production increases ? values between spring and summer, but these increases are partly counteracted by mixing with sea ice melt water and terrestrial river runoff that have low ? values. While these environmental processes play an important role in creating seasonally low saturation states, ocean uptake of anthropogenic CO2 has shifted ? values for aragonite to below the saturation horizon in broad regions across the shelf for at least several months each year. Furthermore, we also report that calcite became undersaturated in September of 2009 in the bottom waters over the shelf. The reduction in CaCO3 mineral saturation states could have profound implications for several keystone calcifying species in the Bering Sea, particularly the commercially important crab fisheries.

Air-sea CO<sub>2</sub> fluxes on the Bering Sea shelf

Abstract. There have been few previous studies of surface seawater CO2 partial pressure (pCO2) variability and air-sea CO2 gas exchange rates for the Bering Sea shelf. In 2008, spring and summertime observations were collected in the Bering Sea shelf as part of the Bering Sea Ecological Study (BEST). Our results indicate that the Bering Sea shelf was close to neutral in terms of CO2 sink-source status in springtime due to relatively small air-sea CO2 gradients (i.e., ΔpCO2 and sea-ice cover. However, by summertime, very low seawater pCO2 values were observed and much of the Bering Sea shelf became strongly undersaturated with respect to atmospheric CO2 concentrations. Thus the Bering Sea shelf transitions seasonally from mostly neutral conditions to a strong oceanic sink for atmospheric CO2 particularly in the "green belt" region of the Bering Sea where there are high rates of phytoplankton primary production (PP)and net community production (NCP). Ocean biological processes dominate the seasonal drawdown of seawater pCO2 for large areas of the Bering Sea shelf, with the effect partly countered by seasonal warming. In small areas of the Bering Sea shelf south of the Pribilof Islands and in the SE Bering Sea, seasonal warming is the dominant influence on seawater pCO2, shifting localized areas of the shelf from minor/neutral CO2 sink status to neutral/minor CO2 source status, in contrast to much of the Bering Sea shelf. Overall, we compute that the Bering Sea shelf CO2 sink in 2008 was 157 ± 35 Tg C yr−1 (Tg = 1012 g C) and thus a strong sink for CO2.

Ocean acidification and biologically induced seasonality of carbonate mineral saturation states in the western Arctic Ocean

Calcium carbonate (CaCO3) mineral saturation states for aragonite (Ωaragonite) and calcite (Ωcalcite) are calculated for waters of the Chukchi Sea shelf and Canada Basin of the western Arctic Ocean during the Shelf‐Basin Interactions project from 2002 to 2004. On the Chukchi Sea shelf, a strong seasonality and vertical differentiation of aragonite and calcite saturation states was observed. During the summertime sea ice retreat period, high rates of phytoplankton primary production and net community production act to increase the Ωaragonite and Ωcalcite of surface waters, while subsurface waters become undersaturated with respect to aragonite due primarily to remineralization of organic matter to CO2. This seasonal “phytoplankton‐carbonate saturation state” interaction induces strong undersaturation of aragonite (Ωaragonite = <0.7–1) at ∼40–150 m depth in the northern Chukchi Sea and in the Canada Basin within upper halocline waters at ∼100–200 m depth. Patches of aragonite undersaturated surface water were also found in the Canada Basin resulting from significant sea ice melt contributions (>10%). The seasonal aragonite undersaturation of waters observed on the Chukchi Sea shelf is likely a recent phenomenon that results from the uptake of anthropogenic CO2 and subsequent ocean acidification, with seasonality of saturation states superimposed by biological processes. These undersaturated waters are potentially highly corrosive to calcifying benthic fauna (e.g., bivalves and echinoderms) found on the shelf, with implications for the food sources of large benthic feeding mammals (e.g., walrus, gray whales, and bearded seals). The benthic ecosystem of the Chukchi Sea (and other Arctic Ocean shelves) is thus potentially vulnerable to future ocean acidification and suppression of CaCO3 saturation states.

Size-fractionated phytoplankton biomass, primary production and respiration in the Nervión–Ibaizabal estuary: A comparison with other nearshore coastal and estuarine ecosystems from the Bay of Biscay

The seasonal pattern of size-fractionated phytoplankton biomass, primary production and respiration was investigated along the longitudinal axis of the Nervión–Ibaizabal estuary (Bay of Biscay) from April 2003 to September 2004. Environmental factors influencing phytoplankton dynamics were also studied. Chlorophyll a biomass showed a longitudinal pattern of increase from the outer Abra bay to the inner estuary. On a seasonal scale, in the intermediate and inner estuary phytoplankton biomass maxima were registered in summer, the warmest and driest season, whereas in the outer bay chlorophyll a peaks occurred in May 2004, but were delayed to August 2003, likely due to a very rainy spring. Data suggest that river flow exerts a marked influence on the timing of phytoplankton biomass maxima in this estuary, decreased river flows providing a lowering of turbidity and an increase in water residence time needed for chlorophyll a to build up. Nutrient concentrations were high enough not to limit phytoplankton growth throughout the annual cycle, except silicate and occasionally phosphate in the outer bay during summer. Silicate concentration correlated positively with river flow, whereas ammonium and phosphate maximum values were generally measured in the mid-estuary, suggesting the importance of allochthonous anthropogenic sources. In the intermediate and inner estuary phytoplankton biomass was generally dominated by >8 μm size-fraction (ca. 60%), but in August 2003 <8 μm size-fraction increased its contribution in the intermediate estuary. It is argued that the lower nutrient concentrations measured in August 2003 than in August 2004 could have played a role. This is the first study in which phytoplankton primary production rates have been measured along the longitudinal axis of the Nervión–Ibaizabal estuary. Throughout the annual cycle these rates ranged from 0.001 to 3.163 g C m −3 d −1 and were comparable to those measured in nearby small estuaries of the Basque coast and other larger estuaries on the Bay of Biscay. Surface plankton community respiration rate maxima were measured during the spring 2004 chlorophyll a peak in the Abra bay and in summer months at the mid and inner estuary, coinciding with chlorophyll a biomass and primary production maxima. In general, respiration rates showed a positive correlation with temperature. In order to compare results from the Nervión–Ibaizabal estuary with other nearshore coastal and estuarine ecosystems within the Bay of Biscay a review of existing information on phytoplankton biomass and primary production dynamics was performed.

Variability of nutrients and phytoplankton primary production in a shallow macrotidal coastal ecosystem (Arcachon Bay, France)

Seasonal and spatial variations of phytoplankton primary production were studied using a high frequency sampling strategy in the external (ENW) and internal (INW) part of Arcachon Bay, during 2002 and 2003. In order to better assess the availability of nutrients and their relationship with phytoplankton primary production, nutrient variability was studied in relation to environmental conditions and phytoplankton production. During winter, when primary production rates were the lowest, nutrient concentrations were maximal but did not show excessive levels compared to highly urbanised areas. Seasonal and spatial variations of nutrient concentrations (especially DIN-nitrate + nitrite + ammonium- and Si) were largely influenced by Leyre River loads coupled with high tidal exchange with the Atlantic Ocean creating a nutrient gradient between the INW and ENW. By February, diatom growth leads to an early severe nutrient depletion in the entire bay. Examination of nutrient ratios showed that the potential limiting nutrient during spring was P in 2003, and Si in 2002. During summer 2003, N and Si concentrations reached their lowest values, and nutrient ratios revealed a N-deficient environment, more pronounced in the INW. The high Si:N ratios during this period might be explained by (1) important N-uptake by all autotroph communities and (2) benthic-pelagic coupling with high Si regeneration. This study shows that nutrient levels in Arcachon Bay seem to play an important role in the control of phytoplankton primary production rates during the productive period and explain their spatial, seasonal and inter-annual variability. Our estimates of annual integrated phytoplankton primary production (103 g C m −2 y −1) place this bay within the low to moderate phytoplankton primary production systems.

Comparative influence of resuspended glacial sediment on physicochemical characteristics and primary production in two arctic lakes

We compared physicochemical properties and rates of phytoplankton and epipelic primary production in two shallow lakes in the Alaskan arctic on eight occasions over three years. The two morphometrically similar lakes lacked defined inlets and had a mean depth of 2.2 m. The lakes differed with respect to glacial influence. Lake GTH 112 was continuously turbid due to resuspension of glacial silt from the lake bed, while GTH 114 showed higher clarity as it was situated on coarser glacial drift. The two lakes contrasted sharply in euphotic zone nutrient concentrations. Soluble reactive phosphorus, NO3−-N and NH4+-N concentrations averaged 0.17, 2.5 and 12.6 μM, respectively, in GTH 112, but were generally at or below the detection limit of 0.05 μM in GTH 114. Reduced light limited the ability of phytoplankton in GTH 112 to use the increased nutrients, and volume-based rates of phytoplankton primary production were similar between lakes. High turbidity in GTH 112 decreased the average percentage of total lake volume and sediment surface within the euphotic zone to 63% and 47%, respectively, compared with values of 88% and 85%, respectively, for GTH 114. Consequently, the average whole lake (phytoplankton plus epipelic) primary production rate in GTH 112 (8.5 mmol m−2 d−1) was significantly lower than the mean rate (12.3 mmol m−2 d−1) for GTH 114. The increase in turbidity affected benthic and pelagic habitats proportionately, as epipelon accounted for about 25% of total whole lake primary production in both lakes.

Phytoplankton Primary Production and Light in Waldo Lake, Oregon

ABSTRACT Waldo Lake is located in the Willamette National Forest along the west side of Oregon's Cascade Mountain Range. The lake is regarded as one of the most oligotrophic lakes in the world, chemically similar to distilled water, with very low rates of phytoplankton primary production and concentrations of chlorophyll a. Historically, vertical light transmission was considerable, with 1% of the lake's incident solar radiation penetrating to depths greater than 60 m. The lake remains exceedingly clear, as demonstrated by transmissometer profiles and Secchi-disk readings that range between 35 and 40 m. Deep chlorophyll maxima are usually found between 60 and 100 m where measurable light is less than 1% of surface illumination. Conversely, primary production rates and assimilation numbers are maximum in the lake's upper 20 m. Unusually large assimilation numbers in the upper 20 m suggests that the phytoplankton that occupy this stratum are photosynthetically efficient, capable of high rates of production with minimal chlorophyll. There are indications, however, that downward irradiance of blue, green and red light has shifted toward a condition in which the attenuation of blue light has increased more than green and red light. This may be attributed to an increase in phytoplankton density, expressed as a roughly 20-fold increase in phytoplankton primary production over the past 25–30 years. On this basis, Waldo Lake may have shifted from an ultraoligotrophic condition to a more eutrophic state.

Waldo Lake, Oregon: Eutrophication of a Rare, Ultraoligotrophic, High-Mountain Lake

ABSTRACT Waldo Lake, Oregon, was described in 1970 as one of the most oligotrophic lakes in the world. But limnological data collected since then indicate that the lake has shifted toward a higher trophic status. This finding is based on three sets of evidence: (1) the spectral distribution of downward irradiance has changed, with blue light now being attenuated more rapidly, while the penetration of both green light and red light has increased; (2) phytoplankton primary production rates have increased 20-fold; and (3) zooplankton have become many times more abundant, and species composition has changed entirely. Although the cause of limnological change is uncertain, investigators believe that it has resulted largely from management and use of the lake. Accordingly, lake visitors have increased dramatically over the past 30 years, from a few hundred visits in 1967 to around 170,000 visits in 1994. Moreover, stocking the lake with 20 million fish between 1938 and 1990 may have disrupted the lake's seemingly fragile ecosystem. Remedial action to save the lake is now being proposed, including (1) repair or removal of sewage-disposal facilities that are possibly defective; (2) tighter restrictions on various lake and watershed uses, and (3) a permanent ban on fish stocking.

Abundance, Biomass, Production and Trophic Roles of Micro- and Net-Zooplankton in Ise Bay, Central Japan, in Winter

We investigated the geographical variations in abundance and biomass of the major taxonomic groups of micro- and net-zooplankton along a transect through Ise Bay, central Japan, and neighboring Pacific Ocean in February 1995. The results were used to estimate their secondary and tertiary production rates and assess their trophic roles in this eutrophic embayment in winter. Ise Bay nourished a much higher biomass of both micro- and net-zooplankton (mean: 3.79 and 13.9 mg C m−3, respectively) than the offshore area (mean: 0.76 and 4.47 mg C m−3, respectively). In the bay, tintinnid ciliates, naked ciliates and copepod nauplii accounted for, on average, 69, 18 and 13% of the microzooplankton biomass, respectively. Of net-zooplankton biomass, copepods (i.e. Acartia, Calanus, Centropages, Microsetella and Paracalanus) formed the majority (mean: 63%). Average secondary production rates of micro- and net-zooplankton in the bay were 1.19 and 1.87 mg C m−3d−1 (or 23.1 and 36.4 mg C m−2d−1), respectively, and average tertiary production rate of net-zooplankton was 0.75 mg C m−3d−1 (or 14.6 mg C m−2d−1). Available data approximated average phytoplankton primary production rate as 1000 mg C m−2d−1 during our study period. The transfer efficiency from primary production to zooplankton secondary production was 6.0%, and the efficiency from secondary production to tertiary production was 25%. The amount of food required to support the zooplankton secondary production corresponded to 18% of the phytoplankton primary production or only 1.7% of the phytoplankton biomass, demonstrating that the grazing impact of herbivorous zooplankton was minor in Ise Bay in winter.

The formation of surface-active organic complexes of copper in coastal marine waters

Abstract The importance of surface-active organic matter on the speciation of copper in coastal seawater was examined over a 22 month period in Massachusetts Bay. Concentrations of copper associated with dissolved surface-active organic matter ranged from 15 pmol kg during winter (0.67% of total dissolved copper) to 850 pmol kg (18% of total dissolved copper) at the peak of primary production during a spring bloom and, following a spring bloom, accounted for 36% of the total dissolved copper concentration. Association of copper with surface-active organic matter may have occurred by direct complexation with surface-active organic ligands or indirectly via organic-organic interactions with non-surface-active organic complexes of copper. Although total dissolved copper at the site was inversely related to salinity, indicative of freshwater/continental sources, the amount of copper bound to surface-active organic matter was significantly correlated with estimated rates of phytoplankton primary production ( r 2 = 0.78). The primary source of surface-active organically bound copper in Massachusetts Bay is apparently in-situ biological production and not export of anthropogenic/freshwater ligands from continental sources. Although they represent a small but significant fraction of the total copper species present in coastal seawater, surface-active forms of copper assume added importance due to their active role in the transport and biogeochemical cycling of this element.