Review: phytoplankton primary production in the world's estuarine-coastal ecosystems

Abstract

Abstract. Estuaries are biogeochemical hot spots because they receive large inputs of nutrients and organic carbon from land and oceans to support high rates of metabolism and primary production. We synthesize published rates of annual phytoplankton primary production (APPP) in marine ecosystems influenced by connectivity to land – estuaries, bays, lagoons, fjords and inland seas. Review of the scientific literature produced a compilation of 1148 values of APPP derived from monthly incubation assays to measure carbon assimilation or oxygen production. The median value of median APPP measurements in 131 ecosystems is 185 and the mean is 252 g C m−2 yr−1, but the range is large: from −105 (net pelagic production in the Scheldt Estuary) to 1890 g C m−2 yr−1 (net phytoplankton production in Tamagawa Estuary). APPP varies up to 10-fold within ecosystems and 5-fold from year-to-year (but we only found 8 APPP series longer than a decade so our knowledge of decadal-scale variability is limited). We use studies of individual places to build a conceptual model that integrates the mechanisms generating this large variability: nutrient supply, light limitation by turbidity, grazing by consumers, and physical processes (river inflow, ocean exchange, and inputs of heat, light and wind energy). We consider method as another source of variability because the compilation includes values derived from widely differing protocols. A simulation model shows that different methods can yield up to 3-fold variability depending on incubation protocols and methods for integrating measured rates over time and depth. Although attempts have been made to upscale measures of estuarine-coastal APPP, the empirical record is inadequate for yielding reliable global estimates. The record is deficient in three ways. First, it is highly biased by the large number of measurements made in northern Europe (particularly the Baltic region) and North America. Of the 1148 reported values of APPP, 958 come from sites between 30° N and 60° N; we found only 36 for sites south of 20° N. Second, of the 131 ecosystems where APPP has been reported, 37% are based on measurements at only one location during one year. The accuracy of these values is unknown but probably low, given the large inter-annual and spatial variability within ecosystems. Finally, global assessments are confounded by measurements that are not intercomparable because they were made with a broad range of methods. Phytoplankton primary production along the continental margins is tightly linked to variability of water quality, biogeochemical processes including ocean-atmosphere CO2 exchange, and production at higher trophic levels including species we harvest as food. The empirical record has deficiencies that preclude reliable global assessment of this key Earth-system process. We face two grand challenges to resolve these deficiencies: (1) organize and fund an international effort to use a common method and measure APPP regularly across a network of coastal sites that are globally representative and sustained over time, and (2) integrate data into a unifying model to explain the wide range of variability across ecosystems and to project responses of APPP to regional manifestations of global change as it continues to unfold.

Marked deleterious changes in the condition, growth and maturity schedules of Acanthopagrus butcheri (Sparidae) in an estuary reflect environmental degradation

“…Thus, while phytoplankton blooms were rarely observed in the 1980s (Zammit et al, 2005), they occurred intermittently in the 1990s (Viney and Sivapalan, 2001) and in most years in the 2000s (Robson and Hamilton, 2003;Hallegraeff et al, 2010;Kristiana et al, 2012). Indeed, this system was one of the two most hypertrophic of the 131 estuarine coastal ecosystems worldwide for which data were recently collated by Cloern et al (2013). The upper reaches of the Swan River Estuary often experience strong stratification during the warm summer months, when freshwater discharge is typically limited and the salt wedge penetrates rapidly along the bottom of the estuary.…”

Size fractionated phytoplankton biomass and net metabolism along a tropical estuarine gradient

“…Primary production rates in tropical estuaries are typically much higher than in temperate ones (Nittrouer et al ; Cloern et al ). These high production rates are due to a comparatively higher nutrient availability, irradiance, and temperature year‐round (Nittrouer et al ).…”

“…Nonetheless, increased turbidity due to high inputs of suspended solids from rivers and sediment resuspension has been shown to limit primary production in many tropical estuaries (Cloern ; Fichez et al ; Nittrouer et al ; Burford et al ). Despite the high phytoplankton productivity in tropical estuaries, many important aspects of phytoplankton ecology have been poorly studied compared with temperate ones (Bianchi ; Burford et al ; Rochelle‐Newall et al ; Cloern et al ). Only in a few cases is there information available on phytoplankton biomass size classes in tropical or subtropical estuaries (Sin et al ; Li et al ; Zhang et al ).…”

A science plan for carbon cycle research in North American coastal waters. Report of the Coastal CARbon Synthesis (CCARS) community workshop, August 19-21, 2014

“…For example, salt marshes, estuaries, and inland waters can exhibit high and variable rates of productivity. The estimated contribution to carbon burial by salt marshes, seagrasses, and mangroves exceeds that in the pelagic ocean (Cloern et al, 2013;Duarte et al, 2005). Factors such as sea level, salinity, nutrient inputs, and tidal forcing can be important environmental drivers (Morris et al, 2013).…”