Edward J. Phlips

Relationships between phytoplankton standing crop and physical, chemical, and biological gradients in the Suwannee River and plume region, U.S.A.

The Suwannee River (USA) is an amber stained, nutrient rich, blackwater river which flows into relatively clear oceanic waters resulting in the formation of a coastal region with unique physical, chemical, and biological gradients. The intent of this study was to describe the spatial and temporal variability of phytoplankton as it relates to these gradients. Ten stations along a transect ranging from 5 km up river to 31 km offshore, were sampled during four different flow regimes. All four sampling periods included in our study of the Suwannee River and plume region exhibited a similar pattern of phytoplankton abundance; low phytoplankton biomass in the Suwannee River and offshore stations with an area of elevated biomass seaward of the Suwannee River outflow. The results of our analysis of light and nutrient limitation in the region support the hypothesis that this spatial pattern of phytoplankton abundance is strongly influenced by color dependent light limitation in the river and outflow area, combined with nutrient limitation offshore. Our results suggest that both light and nutrient availability control abundance and composition of phyto plankton in this coastal area.

Growth, photosynthesis, nitrogen fixation and carbohydrate production by a unicellular cyanobacterium, Synechococcus sp. (Cyanophyta)

A polymer-producing strain of unicellular cyanobacteria, Synechococcus sp., was isolated from a coastal lagoon in Florida. This strain, designated BG0011, excreted a highly viscous polysaccharide. Maximum observed growth rates for BG0011 were 2.5 div. day-2. BG0011 also exhibited nitrogen fixation (nitrogenase) activity under aerobic conditions and grew at near maximum rates in medium lacking reduced nitrogen. Growth and carbohydrate production were enhanced by carbon dioxide enrichment. Rheological study of the extracellular polysaccharide revealed a viscosity versus shear rate curve similar in shape to that of xanthan gum. Maximum observed rate of carbohydrate production was 1 g dry weight liter-1 month-1.

Climatic Influences on Autochthonous and Allochthonous Phytoplankton Blooms in a Subtropical Estuary, St. Lucie Estuary, Florida, USA

The St. Lucie Estuary, located on the southeast coast of Florida, provides an example of a subtropical ecosystem where seasonal changes in temperature are modest, but summer storms alter rainfall regimes and external inputs to the estuary from the watershed and Atlantic Ocean. The focus of this study was the response of the phytoplankton community to spatial and temporal shifts in salinity, nutrient concentration, watershed discharges, and water residence times, within the context of temporal patterns in rainfall. From a temporal perspective, both drought and flood conditions negatively impacted phytoplankton biomass potential. Prolonged drought periods were associated with reduced nutrient loads and phytoplankton inputs from the watershed and increased influence of water exchange with the Atlantic Ocean, all of which restrict biomass potential. Conversely, under flood conditions, nutrient loads were elevated, but high freshwater flushing rates in the estuary diminished water residence times and increase salinity variation, thereby restricting the buildup of phytoplankton biomass. An exception to the latter pattern was a large incursion of a cyanobacteria bloom from Lake Okeechobee via the St. Lucie Canal observed in the summer of 2005. From a spatial perspective, regional differences in water residence times, sources of watershed inputs, and the proximity to the Atlantic Ocean influenced the composition and biomass of the phytoplankton community. Long water residence times in the North Fork region of the St. Lucie Estuary provided an environment conducive to the development of blooms of autochthonous origin. Conversely, shorter residence times in the mid-estuary limit autochthonous increases in biomass, but allochthonous sources of biomass can result in bloom concentrations of phytoplankton.

Aquatic biosystems: reactions and actions

Aquatic biological systems are a critical part of the structure and function of earths biosphere. While attention of the scientific community is often focused on the reaction of biological systems to changes in the environment, these systems also have profound effects, or actions, on the environment. Throughout the evolutionary history of earth, the rise and/or fall of different aquatic biosystems has impacted the character of the biosphere. At no time have environmental changes been more important to all life on earth than in the modern era, which underscores the need for the new journal, Aquatic Biosystems. We welcome submission of original research manuscripts, reviews, and commentaries to the journal.

IMPROVED METHODS FOR THE ISOLATION OF CYANOBACTERIAL DNA FROM ENVIRONMENTAL SAMPLES

DNA isolated from environmental samples often contains enzyme inhibitors disruptive to downstream molecular applications. Most of the existing methods of cyanobacterial DNA isolation do not effectively eliminate these inhibitors from sediment samples or cells collected from freshwater ecosystems. We describe improved methods based on the xanthogenate‐SDS nucleic acid isolation (XS) method of Tillett and Neilan (2000) . Our improved methods provided high‐quality cyanobacterial DNA that could be amplified in PCR and digested with a restriction enzyme. Results were superior to several commercial kits. The DNA yield was also similar to that obtained via the standard XS method. These methods should provide valuable new tools for the expanded application of molecular genetics to limnological and oceanographic research.

Nitrogen fixation by the benthic freshwater cyanobacterium Lyngbya wollei

The ability of the benthic cyanobacterium Lyngbya wollei to fix nitrogen was studied using field samples and axenic cultures. L. wollei was collected and isolated from Lake Okeechobee, Florida, where it forms extensive mats. Rates of acetylene reduction up to 39.1 nmol mg dry wt−1 h−1 were observed for field samples. The maximum observed rate of acetylene reduction in axenic laboratory cultures was 200 nmol mg dry wt−1 h−1. Aerobic conditions limited nitrogen fixation activity, but dark/light cycles promoted the development of activity. Reduced oxygen levels appeared to be required for the development of significant levels of nitrogenase activity. The level of irradiance also had a significant impact on the level of activity. The potential significance of nitrogen fixation to Lyngbya production is discussed.

A Comparison of Water Quality and Hydrodynamic Characteristics of the Guana Tolomato Matanzas National Estuarine Research Reserve and the Indian River Lagoon of Florida

Abstract The lagoons that border the east coast of the Florida peninsula provide an opportunity to study water chemistry and phytoplankton characteristics over a wide range of water residence and nutrient load conditions. This article includes the results of a 2-year study of eight study sites. The northern half of the sampling range included four sampling sites within the newly established Guana Tolomato Matanzas National Estuarine Research Reserve. The southern half of the sampling range consisted of four study sites distributed in ecologically distinct sub-basins of the Indian River Lagoon. The Guana Tolomato Matanzas National Estuarine Research Reserve and Indian River Lagoon include estuaries with water residence times ranging from days to months and watersheds with widely differing nutrient load characteristics. The results of this study revealed wide temporal and spatial variability of physical and chemical characteristics. Mean salinities for the study period ranged from 9.7 to 31.5‰ over the eight sites. Mean orthophosphate and total phosphorus concentrations ranged from 0.26 to 1.55 μM and 1.45 to 3.00 μM, respectively. Mean dissolved inorganic nitrogen and total nitrogen concentrations ranged from 3.14 to 9.77 μM and 26.43 to 71.14 μM, respectively. Individual phytoplankton standing crops, in terms of chlorophyll a concentrations, ranged from less than 1 μg L−1 to more than 60 μg L−1. Comparisons of the relationships between nutrient and phytoplankton standing crops at the eight study sites indicated that water residence times and nutrient loads provided important insights into the basis for observed temporal and spatial patterns of variability. Indices for water residence time and nutrient load were determined for each site. A combination of the character of watershed inputs and residence time was most useful in interpreting patterns of nutrient concentrations, whereas water residence time appeared to be the pre-eminent factor dictating phytoplankton standing crop potential among the eight study sites.

The relationships among phytoplankton biomass, nutrient loading and hydrodynamics in an inner-shelf estuary

Abstract Complex interactions among biological, physical and chemical parameters within coastal ecosystems often make it difficult to define the impacts of nutrient loading on the abundance and distribution of phytoplank-ton biomass. In an effort to address the consequences of nutrient loading, the objective of this study was to define the relationships between changes in nutrient loading and phytoplankton biomass response. The nutrient source to this estuary is the Suwannee River, Florida, U.S.A., which is enhanced in discharge and nitrates by numerous groundwater springs. A network of 18 sites within the river and adjoining coastal environment was sampled monthly from April 1998 to April 2001. The highest phytoplankton biomass in the estuary was observed during periods of elevated riverine discharge and subsequent elevated nutrient loading into the coastal region. In addition, regional variation in phytoplankton biomass was dependent upon residence time within the estuary. The highest standing crops were observed in regions of the estuary subject to the slower flushing rates. Periods of exceptionally high phytoplankton biomass (> 30 μg chl a L-1) were associated with on-shore wind events that increased residence time within the estuary.

The Effects of Sediment Resuspension on Phosphorus Available for Algal Growth in a Shallow Subtropical Lake, Lake Okeechobee

ABSTRACT Algal bioassays were conducted to determine whether phosphorus available for algal growth was released during sediment resuspension in Lake Okeechobee. The bioassays included evaluations of resuspension of sediments at different times of the year. Treatments consisted of floc and surface sediment layers mixed with surface lake water, then filtered to remove all but soluble phosphorus. The presence of phosphorus available for algal growth was manifested as the growth responses of unialgal cultures of phosphorus-starved cyanobacteria isolated from Lake Okeechobee. Floc and sediment treatments caused different algal growth responses depending on the sampling dates. In two summer experiments, there was enhanced growth response of the algae in the surface water previously mixed with sediments and floc. This result contrasted with the winter experiments when algal yields were lower in surface water samples mixed with sediment or floc. The results support recent hypotheses that sediment resuspension in ...

Diversity of and Selection Acting on Cylindrospermopsin cyrB Gene Adenylation Domain Sequences in Florida

ABSTRACT Aphanizomenon ovalisporum is the only confirmed cylindrospermopsin producer identified in the United States to date. On the other hand, Cylindrospermopsis raciborskii is a prominent feature of many lakes in Florida and other regions of the United States. To see the variation in cylindrospermopsin cyrB gene adenylation domain sequences and possibly discover new cylindrospermopsin producers, we collected water samples for a 3-year period from 17 different systems in Florida. Positive amplicons were cloned and sequenced, revealing that approximately 92% of sequences were A. ovalisporum-like (>99% identity). Interestingly, 6% of sequences were very similar (>99% identity) to cyrB sequences of C. raciborskii from Australia and of Aphanizomenon sp. from Germany. Neutrality tests suggest that A. ovalisporum-like cyrB adenylation domain sequences are under purifying selection, with abundant low-frequency polymorphisms within the population. On the other hand, when compared between species by codon-based methods, amino acids of CyrB also seem to be under purifying selection, in accordance with the one proposed amino acid thought to be activated by the CyrB adenylation domain.