Elizabeth M. Cosper

Recurrent and persistent brown tide blooms perturb coastal marine ecosystem

Throughout the summers of 1985 and 1986 a small (2–3 μm diameter), previously underscribed chrysophyte bloomed monospecifically (>109 cells 1−1) in Long Island embayments. The bloom colored the water dark brown, decimated eelgrass beds through decreased light penetration and caused starvation (tissue weight loss) and recruitment failure of commercially important bay scallop populations. These perturbations portend longterm changes in subtidal communities Similar and concurrent blooms in bays of Rhode Island and New Jersey suggest a meteorological component of the environmental conditions promoting bloom formation. Culture experiments with isolates of the microalga suggest the presence of stimulatory growth factors in the bloom seawater. *** DIRECT SUPPORT *** A01BY040 00002

CHARACTERIZATION OF A LYTIC VIRUS INFECTIOUS TO THE BLOOM‐FORMING MICROALGA AUREOCOCCUS ANOPHAGEFFERENS (PELAGOPHYCEAE)

Aureococcus anophagefferens Hargraves and Sieburth has caused recurring monospecific blooms in Long Island embayments since it was first described in 1985. It was termed the “brown tide,” due to the resulting water color, and has had a devastating effect on Long Island’s (New York) marine ecosystem. In 1992, a virus that was capable of causing lysis of A. anophagefferens was isolated and maintained in culture. We report on the further characterization of this virus, Aureococcus anophagefferens virus‐1 (AaV‐1), indicated by a buoyant density of 1.2776 g·mL−1 in a CsCl equilibrium gradient. Electron microscopy revealed a phage with a hexagonal head and tail similar to previously described phages. By using adenovirus for calibration, the virus was found to have a head 50—55 nm wide and a tail 70–75 nm long. The viral band was infectious to A. anophagefferens after dialysis. The virus was composed of at least 16 distinct polypeptides ranging in molecular weight from 20 to 230 kDa. The adsorption coefficient for the virus was 7.2 × 10−9 mL·min−1, and the burst size was calculated to be 9.4 viruses per A. anophagefferens cell at 20° C. Complete lysis of A. anophagefferens occurred with a titer as low as 893 viruses·mL−1, and the lower limit of infectivity was 93 viruses·mL−1. The virus lost its infectivity between 30° and 40° C. These results suggest that AaV‐1 is highly infectious and that the role of the virus in preventing or ending A. anophagefferens blooms needs further investigation.

Viral-like particles (VLPS) in the alga,Aureococcus anophagefferens (pelagophyceae), during 1999–2000 brown tide blooms in Little Egg Harbor, New Jersey

We assessed the presence and quantified the intracellular virus-like particles (VLPs) in natural populations ofAureococcus anophagefferens during the 1999–2000 brown tide blooms that occurred in New Jersey coastal waters. From displayed a wide range of ultrastructural changes from apparently healthy cells to those showing late stages of production of VLPs. VLP-infected cells usually had an electron dense plasma membrane and lacked the typical exocellular polysaccharide layer (EPS). The VLPs were similar in size (c. 140 nm) and morphology to those initially reported in natural populations ofA. anophagefferens and to brown tide viruses (BtVs) which were previously isolated and inoculated into laboratory cultures ofA. anophagefferens. VLP-infectedA. anophagefferens were found consistently throughout the brown tide blooms in both years in Little Egg Harbor. Percentages of VLP-infected cells were 8.1% at the beginning of a bloom, which decreased to less than 2% at the height of the blooms during both years, and increased at the end of the 2000 bloom to 2.5%. While these percentages appear low, the estimated VLP infection rate ofA. anophagefferens cells, which ranged from 0.83%–50% of the standing population, is comparable to other studies.

PCB resistance within phytoplankton populations in polluted and unpolluted marine environments

Abstract A comparison between clones of two species of diatoms, Asterionella japonica and Ditylum brightwellii , isolated from Sandy Hook, New Jersey (polluted site) and Montauk, New York (unpolluted site) indicated that some of the clones from Sandy Hook were more resistant to polychlorinated biphenyls (PCB). A japonica was less sensitive to PCB than D. brightwellii since seven clones of A. japonica from both sites were tolerant of 25 μg litre −1 PCB whereas no clones from either site of D. brightwellii showed such resistance. Growth under high light intensity increased the sensitivity to PCB in all clones except one super-resistant clone from Sandy Hook which was not affected even by additions of 50 μg litre −1 to the growth medium. This interactive effect of light on PCB sensitivity may relate to the photo-adaptive characteristics of each clone.

PCB-resistant diatoms in the Hudson River estuary

Diatom cells that are resistant, as well as sensitive, to the toxicity of polychlorinated biphenyls (PCB) are widespread throughout the highly polluted Hudson River estuary. A study of the distribution of PCB resistance among populations of the diatoms, Thalassiosira nordenskioldii and Asterionella glacialis, revealed few spatial or temporal patterns for the trait during spring and summer. The number of estuarine clones of A. glacialis tolerant of more than 25 ppb of PCB was greater than twice the number of clones isolated from nearshore waters at Sandy Hook, NJ. This suggests that selection pressure for PCB resistance is greater in the estuary than in the New York Bight apex. If specific sites of selection exist, the mixing of cells within the estuary may be rapid enough to distribute resistant clones throughout the estuary, or the selection process may involve a generalized response to a multitude of pollutants. Several clones of both species tested were not only tolerant of PCB, but were actually enhanced in their growth in the presence of PCB. Such clones were distributed throughout the estuary during both seasons. Selection in the estuary favours not only resistant strains of diatoms, but forms that may utilize organic pollutants.

Induced resistance to polychlorinated biphenyls confers cross-resistance and altered environmental fitness in a marine diatom☆

Abstract Since a variety of toxic chemicals is typically found in chronically polluted estuaries, the ability of a marine phytoplankter to develop resistance to polychlorinated biphenyls (PCB), as well as cross-resistance to DDT, was evaluated, as were concomitant alterations of the tolerance to environmental stresses other than pollution, including temperature, salinity and nutrient availability. A clone of the marine diatom, Ditylum brightwellii , sensitive to PCB, was pretreated with sublethal concentrations of PCB over a period of thirty days by two methods: (1) a single dose of 10 μg liter −1 and (2) progressively increasing doses from 10 to 30 μg liter −1 . Both methods produced resistance to PCB, as well as cross-resistance to DDT. Resistance was still present two years later despite no further exposure to PCB. The PCB-resistant strain exhibited greater tolerance to PCB than the PCB-sensitive strain under all environmental conditions where its growth was possible, even at salinities, temperatures and nitrogen levels quite different from those under which resistance was induced. PCB resistance, however, decreased the tolerance of the strain to lower salinities and nitrogen limitation but increased its tolerance to lower temperatures.

Mechanisms Of Resistance to Polychlorinated Biphenyls (PCB) in Two Species of Marine Diatoms

Clones of Ditylum brightwellii and Thalassiosira nordenskioldii were isolated from New York coastal waters, and PCB-resistance in D. brightwellii was induced in the laboratory by exposure to increasing concentrations of PCB. Resistance could not be similarly induced in T. nordenskioldii , but was serendipitously discovered in unexposed cultures that had undergone sexual reproduction. Cells of the resistant strain were substantially larger than those of the sensitive strain in both species. Larger vacuole space seemed to account for this in D. brightwellii , but in T. nordenskioldii larger cells contained more carbon. Experiments with 14 C-PCB tracer indicated that PCB accumulation was less in resistant strains of both species. Neutral lipid content per cell, as determined using the fluorophore Nile Red, was similar for resistant and sensitive strains of both species. Sub-cellular examination of lipid droplets in D. brightwellii suggested that the PCB-resistant strain may be sequestering this lipophilic toxicant in a location removed from physiological activity. In T. nordenskioldii a decreased ratio of neutral lipidxarbon may reduce intracellular accumulation of PCB. These diatom species have developed PCB resistance in the highly PCB-polluted Hudson River estuary and, since they are the preferred food of dominant copepods, they may offer less PCB per unit ration to zooplankton grazers.