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Catalano M.J.,University of Florida | Catalano M.J.,Michigan State University | Allen M.S.,University of Florida | Schaus M.H.,Virginia Wesleyan College | And 2 more authors.
Hydrobiologia | Year: 2010

We evaluated a biomanipulation program to test for short-term changes in water quality (chlorophyll a, Secchi depth, total phosphorus) and macrozooplankton biomass following partial removal of omnivorous gizzard shad Dorosoma cepedianum. The removal occurred at a eutrophic subtropical lake, and responses were compared to an unmanipulated control lake using a before-after-control-impact paired series analysis. The removal reduced the biomass of large (>300 mm) gizzard shad by 75% over 2 years via a subsidized commercial gill net fishery. However, the total population biomass of gizzard shad was reduced by approximately 32% from an average pre-manipulation biomass of 224 kg ha-1 due to the size selectivity of the gear, which did not effectively capture small fish (<300 mm). No significant short-term changes in chlorophyll a concentration, Secchi depth, total phosphorus concentration or macrozooplankton biomass were detected following biomanipulation. The partial removal may have fallen short of the biomass reduction required to cause ecosystem responses. Our results suggest that moderate omnivore removals (i.e., <40% biomass reduction) will have little short-term benefits to these lakes, and future manipulations should use a less size-selective gear to achieve a larger total biomass reduction. © 2010 Springer Science+Business Media B.V.

Havens K.E.,University of Florida | Beaver J.R.,Bsa Environmental Services
Hydrobiologia | Year: 2011

Crustacean zooplankton data were compiled from long-term observational studies at seven large shallow Florida lakes, to determine whether there are general characteristics in regard to species composition, body size, and biomass. In particular, we examined whether patterns in body size and species richness fit empirical models developed by Stanley Dodson. The lakes included range in size from 125 to 1730 km2 and encompass mesotrophic to hyper-eutrophic conditions. We found that zooplankton biomass was strongly dominated by one species of calanoid copepod-Arctodiaptomus dorsalis. Large daphnids were absent, and Cladocera assemblages were dominated by small taxa such as Ceriodaphnia, Chydorus, and Eubosmina. The total number of species of pelagic cladocerans (8-12) was consistent with Dodson's predictions based on lake area. The average size of crustacean zooplankton in Florida lakes is small in comparison with temperate communities. A. dorsalis is the smallest calanoid copepod in North America, and the mean length of Cladocera (0.6 mm) is consistent with Dodson's results that size decreases from temperate to tropical zones. Total biomass of crustacean zooplankton was very low, ratios of zooplankton to phytoplankton biomass (0.01-0.1) are among the lowest reported in the literature, and the zooplankton displayed short-lasting early spring peaks in biomass. Cladocera were almost entirely absent in spring and summer. Factors known to occur in Florida lakes, which appear to explain these characteristics of biomass, include intense fish predation and high summer water temperature. © 2010 Springer Science+Business Media B.V.

Havens K.E.,University of Florida | Beaver J.R.,Bsa Environmental Services | Casamatta D.A.,University of North Florida | East T.L.,South Florida Water Management District | And 4 more authors.
Journal of Plankton Research | Year: 2011

Hurricanes Frances and Jeanne passed over Lake Okeechobee, Florida, in September 2004 and Hurricane Wilma in October 2005. The storms created large waves, strong currents, high wind seiches and uplifted over 3 million metric tons (collectively) of sediments into the water column. Suspended solid concentrations increased five-fold and there were substantial changes in the plankton. Unlike previously documented effects of hurricanes in the open ocean and estuaries, where increased nitrogen inputs stimulate primary productivity, the hurricanes resulted in substantial reductions in biomass of bacteria, phytoplankton and phototrophic nanoflagellates, both in pelagic and near-shore habitats. Increases in macro-zooplankton biomass were observed in both habitats. There were sustained large increases in dissolved inorganic nitrogen and phosphorus in the water column after the hurricanes, coincident with large declines in mean irradiance in the mixed layer. Further, results from laboratory bioassays that exposed the phytoplankton to nutrient additions and a controlled light gradient indicate that the community shifted from being frequently nitrogen limited to most commonly light limited after the storms. The results confirm that the major driver of plankton food-web dynamics in this system is light availability, and that the primary mechanism of change caused by hurricanes is an accentuation of light limitation via greatly increased sediment re-suspension. There additionally was evidence of food-web-mediated effects where the loss of submerged vegetation and increased turbidity reduced the density and efficiency of visually feeding fishes, leading to a significant increase in biomass of macro-zooplankton. © The Author 2011. Published by Oxford University Press. All rights reserved.

Havens K.E.,University of Florida | Beaver J.R.,Bsa Environmental Services
Hydrobiologia | Year: 2013

We examined crustacean zooplankton data (excluding nauplii) from 15 shallow lakes in south and central Florida, spanning a range of sizes and Chlorophyll-a concentrations. Each dataset was comprised of monthly samples from 2 years (6 lakes), or monthly to quarterly samples from 10 or 12 years (9 lakes). We quantified relationships between the zooplankton to phytoplankton biomass ratio (BZ:BP) and measurements of BZ and BP at three levels of resolution: (1) sampling events; (2) seasonal means; and (3) period-of-record means and medians. For individual sampling events, variations in ZB explained most of the variation in BZ:BP and ratios were little affected by changes in BP. Seasonal declines in BZ:BP corresponded with declines in BZ, were not related to declines in biomass of edible algae, and happened in spring-summer when earlier studies indicated high densities of planktivorous fish. Period-of-record means and medians did not identify any relationships between the biomass ratio and either BZ or BP, suggesting that processes affecting the ratio operate at shorter time scales than multiple years. Short-term and seasonal changes in BZ:BP in Florida may be controlled by predation. Testing this hypothesis will require coincident sampling of plankton and fish over a number of years or experimental studies. © 2012 Springer Science+Business Media Dordrecht.

Beaver J.R.,Bsa Environmental Services | Scotese K.C.,Bsa Environmental Services | Minerovic A.D.,Bsa Environmental Services | Buccier K.M.,Bsa Environmental Services | And 2 more authors.
Inland Waters | Year: 2012

We describe characteristics of phytoplankton communities of Ohio reservoirs with emphasis on the interrelationships among cyanobacterial populations, land use within 3 ecoregions, and associated environmental variables. We collected 59 phytoplankton samples from 25 mostly productive reservoirs located within 3 distinct ecoregions corresponding to intense agricultural land use (Eastern Corn Belt Plains), intermediate forestation and intermediate agricultural land use (Erie Drift Plain), and heavily forested land (Western Allegheny Plateau) between May and October 2008-2010 and May and June 2011. Cyanobacteria populations peaked in late summer months and were dominated by nitrogen-fixing taxa only in Western Allegheny Plateau and Erie Drift Plain sites, which commonly included Anabaena, Anabaenopsis, Aphanizomenon, and Cylindrospermopsis. Canonical correlation analysis suggests that the qualitative and quantitative characteristics of phytoplankton populations in Ohio reservoirs are strongly influenced by underlying land use practices. Coarse resolution at the ecoregion scale can be valuable in describing potential cyanobacteria composition where detailed nutrient budgets are not available for particular reservoirs and lakes. © International Society of Limnology 2012.

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