Modeling Nutrient Regeneration in the Ocean with an Aquarium System

Sharp, JH; Frake, AC; Hillier, GB; Underhill, PA

doi:10.3354/meps008015

Cited by 5 publications

(1 citation statement)

References 30 publications

(41 reference statements)

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“…The literature provides less detail on the seasonal behavior of DON than for DIN and PN, but the importance of DON as a bacterial substrate and source of recycled DIN is an accepted fact, and is supported by data from the larger study indicating large and consistent summer bacterial peaks. Our estimate that DON accounts for about 40% of TN in LIS on average is somewhat lower than the estimate (50-64%) of Sharp et al ( 1982) for marine systems in general. Harris ( 1959) reported low DON values one spring, and there was similar evidence in this study, but neither one provided good evidence for a consistent yearly cycle.…”

Section: Processes Consideredcontrasting

confidence: 47%

The planktonic food web structure of a temperate zone estuary, and its alteration due to eutrophication

Capriulo

Smith

Troy

et al. 2002

Nutrients and Eutrophication in Estuaries and Coastal Waters

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Current conventional wisdom argues that human-induced excesses in nutrient loadings to estuaries often stimulate 'excess' algal production leading to hypoxia, via bacterial pathways, and subsequent reduced recruitment/survival of finfish and shellfish. Why wouldn't such elevated production stimulate more animal production, rather than less? In a three-year study of Long Island Sound, U.S.A., a multitude of variables were quantified along a west to east gradient, to address the above question via the hypothesis that different successes among planktonic species experiencing eutrophication alter planktonic food web structure away from traditional pathways to microbial loop dominated ones. Variables studied included: nutrient concentrations and ratios (i.e. N02, N03, NH4, DON, PON, P04, Silicate, NIP and N/Si), phytoplankton, protozooplanktonic ciliate, zooplankton, heterotrophic nanoplankton (HNAN), photosynthetic nanoplankton (PNAN), size-fractionated chlorophyll, larval fish and bacterial concentrations and/or species composition, and bacterial growth rates (as frequency of dividing cells, FDC). Results indicated that although current nitrogen and other nutrient loadings into the estuary are much higher than past inputs (especially in western waters), the average concentration of dissolved inorganic nutrients is similar (though slightly higher) to past values. Relative proportioning among chemical species does vary from west to east, with NH4 and dissolved organic nitrogen (DON) at times more prevalent in the west, especially in bottom waters. Excess loadings of nitrogen and other nutrients into the estuary are converted to elevated biomass of both small ( < I 0 f.Lm), and large (>20 f.Lm) phytoplankton in the west. Slightly enhanced bacterial densities and growth rates shadow the elevated chlorophyll levels, with distinctive Sound-wide seasonal patterns that follow not total chlorophyll, but rather PNAN concentrations. HNAN concentrations also are elevated in the west, and likely influence bacterial dynamics. Species composition of phytoplankton routinely differ west to east. Inorganic NIP are routinely low (i.e. below Redfield ratios), especially in the west, while total dissolved N/P (i.e. including DON) are similar among stations and typically are significantly higher than Redfield ratios. Associated with bacterial and < 10 f.Lm chlorophyll enhancements to an elevated diversity of ciliate species in the west. Copepod biomass is extremely enhanced in the west, indicating that while stimulating the microbial loop, eutrophication is also enhancing the secondary production preferred by larval fish and gelatinous zooplankton. Larval fish diversity is down relative to the past, but shows little contemporaneous west/east variations. So, if adult fish populations are down, but larvae are not food limited, possibly toxicity, overfishing, and/or habitat destruction which prevent a healthy, normal system response to eutrophication are culpable. It is suggested that recipients of the excess copepod production are ...

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Section: Processes Consideredcontrasting

confidence: 47%