Larry E. Brand

Reduction of marine phytoplankton reproduction rates by copper and cadmium

Abstract The reproduction rates of 38 clones of marine phytoplankton were measured in media in which free cupric ion activity was controlled at different levels using a NTA-cupric ion buffer system. The major trend among species in their resistance to copper toxicity was a phylogenetic one, with cyanobacteria being the most sensitive, diatoms the least sensitive, and coccolithophores and dinoflagellates intermediate in sensitivity. The reproduction rates of most of the cyanobacteria were reduced at cupric ion activities above 10 −12 M, while most eukaryotic algae still had maximum reproduction rates at 10 −11 M. Four species, Emiliana huxleyi (Lohm.) Hay & Mohler, Skeletonema costatum (Grev.) Cleve, Thalassiosira pseudonana (Hustedt) Hasle & Heimdal and Thalassiosira oceanica (Hustedt) Hasle were particularly resistant to copper, being able to reproduce well at the highest cupric ion activities tested, 10 −9.5 M and 10 −9.2 M. There was no major difference, however, between neritic and oceanic species in their sensitivity to copper. The sensitivity of 20 species of marine phytoplankton to free cadmium ion activity was measured in a similar manner using an NTA-cadmium ion buffer system. As observed with copper, the prokaryotic cyanobacteria were the most sensitive to cadmium toxicity, diatoms were the least sensitive, and coccolithophores and dinoflagellates were intermediate. All cyanobacteria tested were dead at a cadmium ion activity of 10 −9.3 M whereas the reproduction rates of most of the eukaryotic algae were not reduced significantly until 10 −8.3 M. Comparison of these data with natural concentrations in sea water implies that cadmium is not an important ecological factor in unpolluted waters but natural copper concentrations may inhibit the reproduction of some phytoplankton species, especially cyanobacteria, in upwelled sea water. Copper may influence the seasonal succession of species.

Distribution and potential sources and sinks of copper chelators in the Sargasso Sea

Abstract Copper speciation has been studied at an oligotrophic station in the southwestern Sargasso Sea to determine the distribution of Cu binding ligands and evaluate their potential sources and sinks. Speciation was studied using a ligand exchange/liquid-liquid partition procedure used in a previous study in Florida coastal waters [ Moffet and Zika (1987a) Marine Chemistry, 21, 301–313]. Copper speciation was dominated by organic complexation at all depths studied (16–950 m). Complexation was greatest in the region of the chlorophyll maximum. In this region, speciation was dominated by two ligands or ligand classes; L1, with Kcond. = 1013.2, concentration = 2 nM, and a weaker but more abundant ligand class, L2 with Kincond. = 109.7, concentration = 80 nM. From 140 to 16 m, [Cu(II)]free/[Cu(II)]total increases by a factor of 20, due to a decrease in [L1] to a value below the ambient Cu concentration. Exposure of water from 140 m to sunlight indicated that photochemical decomposition of L1 may account for the decrease. Below the chlorophyll maximum there is a gradual increase in [Cu(II)]free/[Cu(II)]total suggesting that the ligands are of recent biological origin rather than derived from refractory materials. Cultures of a ubiquitous marine cyanobacterium, Synechococcus sp. produced a ligand with Kcond. comparable to L1, indicating that a biological source is plausible.

The effects of continuous light and light intensity on the reproduction rates of twenty-two species of marine phytoplankton☆

Abstract The acclimated reproduction rates of 22 species of marine phytoplankton were measured at 0.01, 0.023, 0.1, and 0.23 ly/min in continuous light and in a 14: 10 h light: dark cycle. Three species that reproduced exponentially at all four light intensities in the 14: 10 LD regime did not reproduce at all in continuous light at any of the light intensities. One species, which reproduced at the two lowest light intensities in the 14: 10 LD regime, failed to reproduce at all in continuous light at any light intensity examined. Seven species reproduced more slowly in continuous light than in the 14: 10 LD regime at most or all light intensities. Four species reproduced at roughly the same rate in both light regimes. Five species reproduced more rapidly in continuous light. No general phylogenetic trend could be discerned from the responses of the species to the different light intensities or to continuous light. In general, species from coastal regions can reproduce as rapidly or more rapidly in continuous light than in a 14: 10 LD cycle, while most species from oceanic regions are harmed by continuous light. A phylogenetic trend in maximum potential reproduction rate is apparent, with diatoms being the fastest, dinoflagellates the slowest, and coccolithophores somewhat intermediate.

The salinity tolerance of forty-six marine phytoplankton isolates

Abstract The acclimated reproduction rates of 46 marine phytoplankton isolates were measured in six salinities ranging from 0 to 45%. Estuarine species tolerated low salinity better than the oceanic species, coastal species being intermediate in their tolerance. The estuarine and oceanic species had salinity tolerances appropriate for their environments, but most of the coastal species tolerated salinity much lower than that from which they were isolated. This characteristic of coastal species may be a relict of selection pressure during the most recent glaciation or the result of gene flow being dependent upon central genetic populations located in bays and estuaries.

Measurement of vertical distribution of isoprene in surface seawater, its chemical fate, and its emission from several phytoplankton monocultures

Abstract Concurrent measurements of isoprene (2-methyl-1,3-butadiene) in seawater together with atmospheric concentrations in the Gulf Stream off the Florida coast were made. Florida Straits surface water concentrations of isoprene varied between 9.8 and 50.8 pmol 1 −1 . Surface water isoprene concentrations showed a positive correlation with measured chlorophyll fluorescence, consistent with the biogenic origin of this non-methane hydrocarbon. Depth profiles showed a maximum in isoprene concentration similar to that of biological productivity as indicated by chlorophyll fluorescence. Daytime atmospheric mixing ratios of isoprene were never above 11 parts-per-trillion (pptv) and eight of eleven samples taken were below the ~ 5 pptv detection limit. Using an estimated value of the Henrys law constant ( K H ~ 3.1) a supersaturation of surface seawater of 2 to 3 orders of magnitude is estimated. Laboratory grown monocultures of several common phytoplankton species showed production of isoprene. Processes controlling the isoprene concentration in the photic zone of the ocean and the marine boundary layer are discussed. A calculation using a simple time dependent photochemical box model confirmed that isoprene is rapidly consumed by its reaction with the OH radical in the marine atmosphere.

Thoracosphaera heimii (Lohmann) Kamptner Is a Dinophyte: Observations on Its Morphology and Life Cycle

Abstract Thirty clones of Thoracosphaera heimii (Lohmann) Kamptner have been isolated and cultured from oceanic waters of the western North Atlantic and Gulf of Mexico. Observations on the life cycle and morphology of one clone isolated from the Sargasso Sea are reported herein. The calcareous cell wall is present in the coccoid, vegetative life phase. Reproduction is accomplished by the formation of transitory aplanospore or planospore stages or occasionally by binary fission of weakly calcified cells. The planospore is non-thecate and Gymnodinium-like with an undulating transverse flagellum and a whip-like longitudinal flagellum. All life stages possess chloroplasts and a nucleus with continually condensed chromosomes. The planospore morphology and the dinocaryotic nucleus demonstrate that T. heimii is a dinophyte and not a coccolithophorid. The taxonomic affinity and classification of T. heimii within the Dinophyceae is discussed and a new order Thoracosphaerales Tangen, ord. nov. is proposed for primarily coccoid marine dinoflagellates that possess a calcified cell wall in the vegetative life phase.

Stable isotopic composition of coccoliths

Oxygen isotope analyses of coccoliths from eight coccolithophore species grown in laboratory culture indicate that biological fractionation occurs during the formation of calcium carbonate. Cultures of coccolithophores, including species not previously grown in the laboratory were maintained at various temperatures ranging from 12–28°C. Over this range of temperature, oxygen isotope values for Emiliania huxleyi, Gephyrocapsa oceanica, and Crenalithus sessilis are found to be 1‰ enriched in 18O relative to calcium carbonate precipitated under equilibrium conditions. Coccoliths of Calcidiscus leptoporus, Umbilicosphaera sibogae, U. hulburtiana, Syracosphaera pulchra, and Cricosphaera carterae were found to be 2.5‰ depleted in 18O relative to equilibrium. These findings help clarify previously reported equivocal oxygen isotope data derived from sedimentary calcareous nannofossils and reveal the importance of species-specific isotopic fractionation.

CELL DIVISION PERIODICITY IN 13 SPECIES OF MARINE PHYTOPLANKTON ON A LIGHT: DARK CYCLE1

The division rates of 26 clonal cultures representing 13 species of planktonic marine algae (6 diatoms, 2 flagellated chrysophytes, 2 coccolithophores, 1 cryptomonad flagellate, I dinoflagellate, 1 green alga) were determined every 2 h for 48 h during exponential growth on a 14:10 LD cycle in nutrient‐replete batch culture. Cyclic oscillations in the division rate were detectable in 22 of these clones. Of 14 diatom clones examined, four displayed nearly constant division rates throughout the LD cycle and ten showed strong periodicity favoring division during the light periods. In contrast, all other algae (12 clones) exhibited division rate maxima during periods of darkness, and clearly detectable decreases in cell number for time intervals of 4–8 h during periods of illumination. Intraspecific differences in division periodicity were found among eight clones of the diatom Thalassiosira pseudonana (Hustedt) Hasle & Heimdal and six clones of the coccolithophore Emiliania huxleyi (Lohm.) Hay & Mohler.

Impacts of Hurricanes Katrina and Rita on the microbial landscape of the New Orleans area

Floodwaters in New Orleans from Hurricanes Katrina and Rita were observed to contain high levels of fecal indicator bacteria and microbial pathogens, generating concern about long-term impacts of these floodwaters on the sediment and water quality of the New Orleans area and Lake Pontchartrain. We show here that fecal indicator microbe concentrations in offshore waters from Lake Pontchartrain returned to prehurricane concentrations within 2 months of the flooding induced by these hurricanes. Vibrio and Legionella species within the lake were more abundant in samples collected shortly after the floodwaters had receded compared with samples taken within the subsequent 3 months; no evidence of a long-term hurricane-induced algal bloom was observed. Giardia and Cryptosporidium were detected in canal waters. Elevated levels of fecal indicator bacteria observed in sediment could not be solely attributed to impacts from floodwaters, as both flooded and nonflooded areas exhibited elevated levels of fecal indicator bacteria. Evidence from measurements of Bifidobacterium and bacterial diversity analysis suggest that the fecal indicator bacteria observed in the sediment were from human fecal sources. Epidemiologic studies are highly recommended to evaluate the human health effects of the sediments deposited by the floodwaters.

Centers for Oceans and Human Health: a unified approach to the challenge of harmful algal blooms

BackgroundHarmful algal blooms (HABs) are one focus of the national research initiatives on Oceans and Human Health (OHH) at NIEHS, NOAA and NSF. All of the OHH Centers, from the east coast to Hawaii, include one or more research projects devoted to studying HAB problems and their relationship to human health. The research shares common goals for understanding, monitoring and predicting HAB events to protect and improve human health: understanding the basic biology of the organisms; identifying how chemistry, hydrography and genetic diversity influence blooms; developing analytical methods and sensors for cells and toxins; understanding health effects of toxin exposure; and developing conceptual, empirical and numerical models of bloom dynamics.ResultsIn the past several years, there has been significant progress toward all of the common goals. Several studies have elucidated the effects of environmental conditions and genetic heterogeneity on bloom dynamics. New methods have been developed or implemented for the detection of HAB cells and toxins, including genetic assays for Pseudo-nitzschia and Microcystis, and a biosensor for domoic acid. There have been advances in predictive models of blooms, most notably for the toxic dinoflagellates Alexandrium and Karenia. Other work is focused on the future, studying the ways in which climate change may affect HAB incidence, and assessing the threat from emerging HABs and toxins, such as the cyanobacterial neurotoxin β-N-methylamino-L-alanine.ConclusionAlong the way, many challenges have been encountered that are common to the OHH Centers and also echo those of the wider HAB community. Long-term field data and basic biological information are needed to develop accurate models. Sensor development is hindered by the lack of simple and rapid assays for algal cells and especially toxins. It is also critical to adequately understand the human health effects of HAB toxins. Currently, we understand best the effects of acute toxicity, but almost nothing is known about the effects of chronic, subacute toxin exposure. The OHH initiatives have brought scientists together to work collectively on HAB issues, within and across regions. The successes that have been achieved highlight the value of collaboration and cooperation across disciplines, if we are to continue to advance our understanding of HABs and their relationship to human health.