Calibration of a Water-Quality Model for Herrington Lake Using Empirically Derived Measurements of Phytoplankton Growth and Nutrient Assimilation

Importance of light limitation, nutrient availability, and hydrology in controlling the abundance and composition of the phytoplankton community of Herrington Lake (KY) was investigated over a two-year period. Selected environmental parameters were measured every two weeks (April-October) at five sampling stations located along the longitudinal gradient of the reservoir. In addition, short-term (48hr) nutrient enrichment experiments were conducted to assess the spatial and temporal variations in nutrient limitation. Phytoplankton growth responses to the combined addition of nitrogen (NO3) and phosphorus (PO4) were greater than those resulting from the addition of either nutrient alone. These results indicate that phytoplankton production was closely co-limited by the availability of both N and P. The magnitude of the phytoplankton responses to nutrient additions was greatest at downstream stations and in late summer suggesting that those populations experience more severe nutrient limitation. Significant interannual variations in nutrient limitation and primary production were observed during this study period (1995-1996). In 1995, nutrient limitation was more severe than in 1996. Above average rainfall and discharge in 1996 coincided with increased productivity (mg C/m3/hr) and minimal nutrient limitation. Phytoplankton community composition showed similar patterns of seasonal succession in both years

Algal toxins in the food chain – a comparative study of Chesapeake Bay and Baltic coastal food webs

Microcystin (MC) is a hepatotoxin produced by cyanobacteria (blue-green algae) which is found globally in eutrophic waters including lakes, lagoons and estuaries (Paerl and Paul 2012). The presence of MC in food webs is of concern due to adverse effects on biota and exposure to humans via commercial and recreational fisheries (Paerl and Otten 2013). Little is known regarding the factors which determine MC accumulation in food webs. We hypothesized that dietary exposure would be determined in part by sources of organic matter supporting the food web. We undertook a comparative study of the James River Estuary, a sub-estuary of Chesapeake Bay, and the Curonian Lagoon, a sub-estuary of the Baltic Sea and largest coastal lagoon in Europe. Both sites experience cyanobacteria blooms known to produce MC (Wood et al. 2014; Lesutienė et al. 2014), but differ in their sources of organic matter. The James receives large inputs of terrestrial organic matter due to the draining of a mountainous catchment. The Curonian Lagoon is fed by a lowland river which delivers low concentrations of terrestrial organic matter. We hypothesized that high internal production in the lagoon, coupled with lower dilution by terrestrial organic matter inputs, would results in greater exposure to MC among biota of the Curonian Lagoon

Spatial Variation among Lakes within Landscapes: Ecological Organization along Lake Chains

Although limnologists have long been interested in regional patterns in lake attributes, only recently have they considered lakes connected and organized across the landscape, rather than as spatially independent entities. Here we explore the spatial organization of lake districts through the concept of landscape position, a concept that considers lakes longitudinally along gradients of geomorphology and hydrology. We analyzed long-term chemical and biological data from nine lake chains (lakes in a series connected through surface or groundwater flow) from seven lake districts of diverse hydrologic and geomorphic settings across North America. Spatial patterns in lake variables driven by landscape position were surprisingly common across lake districts and across a wide range of variables. On the other hand, temporal patterns of lake variables, quantified using synchrony, the degree to which pairs of lakes exhibit similar dynamics through time, related to landscape position only for lake chains with lake water residence times that spanned a wide range and were generally long (close to or greater than 1 year). Highest synchrony of lakes within a lake chain occurred when lakes had short water residence times. Our results from both the spatial and temporal analyses suggest that certain features of the landscape position concept are robust enough to span a wide range of seemingly disparate lake types. The strong spatial patterns observed in this analysis, and some unexplained patterns, suggest the need to further study these scales and to continue to view lake ecosystems spatially, longitudinally, and broadly across the landscape.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42434/1/10021-2-5-395_2n5p395.pd

Drivers of Cyanobacterial Blooms in a Hypertrophic Lagoon

The Curonian Lagoon is Europe's largest lagoon and one of the most seriously impacted by harmful blooms of cyanobacteria. Intensive studies over the past 20 years have allowed us to identify the major drivers determining the composition and spatial extent of hyperblooms in this system. We summarize and discuss the main outcomes of these studies and provide an updated, conceptual scheme of the multiple interactions between climatic and hydrologic factors, and their influence on internal and external processes that promote cyanobacterial blooms. Retrospective analysis of remote sensed images demonstrated the variability of blooms in terms of timing, extension and intensity, suggesting that they occur only under specific circumstances. Monthly analysis of nutrient loads and stoichiometry from the principal tributary (Nemunas River) revealed large interannual differences in the delivery of key elements, but summer months were always characterized by a strong dissolved inorganic N (and Si) limitation, that depresses diatoms and favors the dominance of cyanobacteria. Cyanobacteria blooms occurred during high water temperatures, long water residence time and low-wind conditions. The blooms induce transient (night-time) hypoxia, which stimulates the release of iron-bound P, producing a positive feedback for blooms of N-fixing cyanobacteria. Consumer-mediated nutrient recycling by dreissenid mussels, chironomid larvae, cyprinids and large bird colonies, may also affect P availability, but their role as drivers of cyanobacteria blooms is understudied

Migratory patterns and cyanotoxin concentrations of pikeperch (Sander lucioperca) in the coastal waters of the Baltic Sea

We used stable isotopes of sulfur (δ34S) and carbon (δ13C) to distinguish resident and migratory pikeperch (Sander lucioperca) among individuals captured from a coastal freshwater lagoon (Curonian Lagoon) and adjacent Baltic Sea waters. We found that non-migratory pikeperch collected from the lagoon had negative δ34S ratios (–1.84‰ to –0.17‰), whereas migrating individuals exhibited higher and more variable δ34S values (4.4‰ to 18.5‰). Our findings suggest that S isotopes may be a valuable tool for assessing migratory habits in the brackish waters. We also compared cyanotoxin concentrations among the resident individuals of Curonian Lagoon and the migratory individuals in or returning from the Baltic Sea. No difference in toxin levels was observed among the resident and migratory pikeperch, although toxin concentrations were frequently close to or exceeded the recommended concentrations for safe long-term human consumption

Migratory patterns and cyanotoxin concentrations of pikeperch (Sander lucioperca) in the coastal waters of the Baltic Sea

We used stable isotopes of sulfur (δ34S) and carbon (δ13C) to distinguish resident and migratory pikeperch (Sander lucioperca) among individuals captured from a coastal freshwater lagoon (Curonian Lagoon) and adjacent Baltic Sea waters. We found that non-migratory pikeperch collected from the lagoon had negative δ34S ratios (–1.84‰ to –0.17‰), whereas migrating individuals exhibited higher and more variable δ34S values (4.4‰ to 18.5‰). Our findings suggest that S isotopes may be a valuable tool for assessing migratory habits in the brackish waters. We also compared cyanotoxin concentrations among the resident individuals of Curonian Lagoon and the migratory individuals in or returning from the Baltic Sea. No difference in toxin levels was observed among the resident and migratory pikeperch, although toxin concentrations were frequently close to or exceeded the recommended concentrations for safe long-term human consumption