Local primary production hotspot in the coastal waters of Southampton Island, Nunavut, Canada, in summer 2019

Environmental control of summer primary production in the Hudson Bay system: The role of stratification

Primary productivity plays a key role in aquatic lake ecosystems. This study addresses the characteristics of primary phytoplankton productivity and its relationship with environmental factors in a large, shallow, and eutrophic lake (Lake Taihu, China). Surface water samples were collected in wet and dry seasons from eight lake areas to investigate physicochemical factors and primary productivity. The results show obvious seasonal differences in phytoplankton primary productivity and physicochemical factors in Lake Taihu. The primary productivity in the wet season is about five times larger than that in the dry season, and the spatial distribution of primary productivity is obviously inhomogeneous in the wet season, while in the dry season, there are no significant differences in different lake areas. Most of the lake areas are in the middle eutrophic state regardless of the season; the northwest region has the heaviest degree of eutrophication, while the southeast region has the lightest degree of eutrophication. Pearson correlation indicated that nutrients are the main factors affecting primary productivity in the wet season, while temperature is the most important factor affecting primary productivity in the dry season. Multiple stepwise regression suggested that chlorophyll-a (Chl-a), temperature (T), and water transparency (SD) can be used to estimate the phytoplankton primary productivity in Lake Taihu in different seasons, and the main influencing factors for primary productivity are Chl-a, nutrients, and SD/total suspended solids (TSS) in the wet season and T, Chl-a, and SD/TSS in the dry season.

太湖湖岸带浮游植物初级生产力特征及影响因素

A PRELIMINARY ACCOUNT OF LATE "WISCONSIN" GLACIATION IN MELVILLE PENINSULA, N.W.T.*

浮游植物初级生产力是评估水产养殖系统结构与功能的基础环节，对渔业资源的开发与管理具有重要意义.于2018年5—10月，采用黑白瓶法对闽江河口区的3个南美白对虾养殖塘（PondⅠ、PondⅡ和PondⅢ）水体浮游植物初级生产力进行了原位监测，初步研究了初级生产力在池塘间的差异性及其时间变化特征.结果显示，养殖期间养殖塘水体浮游植物总初级生产力（GPP）、呼吸消耗量（R_P）和净初级生产力（NPP）变化范围分别为619.99~9498.67、1003.16~7063.33和-4179.50~6362.96 mg O₂/（m²·d），均值分别为（4386.22±409.72）、（3607.53±150.27）和（778.68±260.16） mg O₂/（m²·d），呈现出Pond Ⅱ>Pond Ⅲ>PondⅠ的特征.时间变化上，养殖塘水体浮游植物GPP和NPP呈现出随养殖阶段推移而增加的特征.多元逐步回归分析结果显示，N营养盐和叶绿素a浓度是影响养殖塘水体浮游植物初级生产力时空变化的主要因子.GPP/R_P系数在养殖初期小于1，而在养殖中后期大于1，表明养殖塘水体在养殖初期以异养生产为主，而中后期以自养生产为主.本文研究结果表明，今后在开展大尺度滨海水产养殖塘初级生产力精确评估及其相关模型参数构建时，需考虑池塘间水体初级生产力的时间变化特征.;The phytoplankton primary productivity is a great basis to evaluate the structure and function of aquaculture ecosystem, which qualify important significance for fishery resources exploitation. In this study, we measured the phytoplankton primary productivity among shrimp (Litopenaeus vannamei) ponds during the aquaculture periods in the Minjiang River estuary, Southeast China. The results showed that the gross primary production (GPP), respiration (R_P) and net primary production (NPP) of phytoplankton among ponds over the shrimp aquaculture period varied from 619.99 to 9498.67, 1003.16 to 7063.33, and -4179.50 to 6362.96 mg O₂/(m²·d) respectively, with mean values of (4386.22±409.72), (3607.53±150.27) and (778.68±260.16) mg O₂/(m²·d) respectively. Overall, the mean GPP, R_P and NPP decreased significantly among the three ponds in the order:PondⅡ > PondⅢ > PondⅠ. The phytoplankton primary productivity demonstrated a clear seasonal pattern, with an increasing trend with time. Multiple stepwise regression analysis showed that nitrogen nutrient and chlorophyll-a were the major impact factors of the spatiotemporal variations of phytoplankton primary productivity in shrimp ponds. Our results highlighted that the importance of considering the spatiotemporal variations in primary productivity in improving the accuracy of large-scale estimation of phytoplankton primary productivity in coastal aquaculture pond.

A study of in situ primary productivity (light- and dark-bottle oxygen exper- iments) was conducted biweekly in 1990 and 1991 to measure volumetric rates of phytoplankton photosynthesis and estimate integral phytoplankton photosynthesis and primary production. Concurrently, ambient conditions including water temperature, photosynthetically active radiation (PAR), Secchi disc transparency, dissolved oxygen and phytoplankton biomass (chlorophyll- a) were measured. Results of both light- and dark-bottle experiments are used to 1) demonstrate that Lake Apopka is not hetero- trophic as reported in the literature, 2) provide preliminary estimates of phytoplankton primary production, 3) discuss shortcomings in experimental methodology and 4) evaluate sources of temporal variability in phytoplankton primary production. No strong seasonal patterns were found in ambient physical and chemical conditions with the exception of water temperature. Whole-basin estimates of net organic carbon sedi- mentation are used as an independent approach to estimate phytoplankton primary pro- duction. The magnitude of net primary production ranged from approximately 1 to 2gCm -2 d -1 for three direct estimates and from to 3 to 5gC m -2 d -1 for the indirect method. We conclude that short-term temporal variability in primary productivity is controlled mainly by meteorological forcing of wind-induced turbulence and resuspen- sion of meroplankton. Our study shows that obtaining precise and accurate direct esti- mates of phytoplankton photosynthesis and production are more complex than might be anticipated from the application of standard techniques.

Biological and physicochemical factors controlling short-term variability in phytoplankton primary production and photosynthetic parameters in a macrotidal ecosystem (eastern English Channel)

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

The seasonal and long-term dynamics of phytoplankton primary production has been studied in the Rybinsk Reservoir (Upper Volga) in 2005–2014. A positive correlation has been found to exist between the values of plankton primary production, averaged over vegetation period, and the abiotic factors of the water medium (temperature, solar radiation, and nutrient concentrations), as well as, excluding the data on the anomalously hot summer of 2010, between the primary production and the index of North Atlantic Oscillation. The increase in water temperature (up to 27.9°C) in the summer of 2010 has caused a considerable increase in phytoplankton production. A considerable increase in phytoplankton primary production has been revealed in the Rybinsk Reservoir in the period under study.

Physical science

Seasonal variations in phytoplankton biomass and primary production in the Ethiopian Rift Valley lakes Ziway, Awassa and Chamo – The basis for fish production

基于VGPM模型和MODIS数据估算梅梁湾浮游植物初级生产力

Primary production within the sea-ice zone west of the Antarctic Peninsula: I—Sea ice, summer mixed layer, and irradiance

The summer distribution of sea ice meltwater and river runoff and the surface circulation in Foxe Basin, Hudson Bay, and Hudson Strait have been studied by oxygen isotope techniques. On the basis of oxygen isotope and salinity relationships, the reduction of surface salinity in summer in Foxe Basin is predominantly due to sea ice meltwater. River runoff and sea ice meltwater contribute equally to the summer surface layer in northern Hudson Bay. The isotopic data clearly show the flow of Foxe Basin water through Roes Welcome Sound into northwestern Hudson Bay, but no evidence for this outflow is found in the passages connecting Hudson Bay and Hudson Strait. Oxygen isotopes indicate that recent river runoff is concentrated in a narrow band along the south side of Hudson Strait. The wide variety of relationships between oxygen isotope ratios and salinity is explained by the known ice dynamics and the seasonal variability predicted from ice melting and freezing models.

This study documents the results of a multi-sensor satellite investigation aimed at comparing the seasonality and interannual variability of phytoplankton biomass and primary productivity (PP) in the western and eastern gyres of the subarctic Pacific. Satellite data helped discern several features, most importantly the existence of significant east-west gradients in the supply of nitrate in winter, in the consumption of nitrate by phytoplankton and in phytoplankton production and biomass accumulation over the growth season. In the western subarctic gyre many of these features appear to be regulated by the strength of sea surface winds through increased iron and nitrate inputs. Multiple regression analysis of data extracted from 12 boxes spanning different hydrographic regimes in the subarctic Pacific, showed that over 65% of the variations in PP in the subarctic Pacific could be explained solely on the basis of changes in the strength of sea surface winds and the intensity of incident irradiance (PAR). The dependence of PP on sea surface wind stress was far greater in the western subarctic Pacific Gyre (WSG), than in the Alaskan Gyre (ALG) due to diminishing impact of surface winds towards the east. Spring accumulation of phytoplankton biomass was greater in the WSG than in the ALG despite the higher rates of PP in the latter. This study assumes particular significance because it helps ascertain the existence of several sub-regions within the two broader domains of the WSG and the ALG. In addition, large interannual variations in phytoplankton biomass and PP were observed in the subarctic Pacific following the onset of the El-Nino event of 1997 and the transition to La-Nina conditions in 1999. These variations were largely the result of differences in meteorological and oceanographic conditions across the subarctic Pacific following the development of the El-Nino.