Nutrient-poor Waters Research Articles

Deletion of oxyR in Legionella pneumophila causes growth defect on agar.

The intracellular pathogen Legionella pneumophila (Lp) is a strict aerobe, surviving and replicating in environments where it frequently encounters reactive oxygen species (ROS), such as the nutrient-poor water environment and its replicative niche inside host cells. In many proteobacteria, the LysR-type regulator OxyR controls the oxidative stress response; however, the importance of the OxyR homologue in Lp is still unclear. Therefore, we undertook the characterization of phenotypes associated with the deletion of oxyR in Lp. Contrary to the wild type, the oxyR deletion mutant exhibits a severe growth defect on charcoal - yeast extract (CYE) agar lacking α-ketoglutarate supplementation. Growth in AYE broth (CYE without agar and charcoal), in amoeba and in human cultured macrophages, and survival in water is unaffected by the deletion. Supplementing CYE agar with antioxidants that neutralize ROS or introducing the oxyR gene in trans rescues the observed growth defect. Moreover, the mutant grows as well as the wild type on CYE plates made with agarose instead of agar, suggesting that a compound present in the latter is responsible for the growth defect phenotype.

Testing Wallace's intuition: water type, reproductive isolation and divergence in an Amazonian fish.

Alfred Russel Wallace proposed classifying Amazon rivers based on their colour and clarity: white, black and clear water. Wallace also proposed that black waters could mediate diversification and yield distinct fish species. Here, we bring evidence of speciation mediated by water type in the sailfin tetra (Crenuchus spilurus), a fish whose range encompasses rivers of very distinct hydrochemical conditions. Distribution of the two main lineages concords with Wallace's water types: one restricted to the acidic and nutrient-poor waters of the Negro River (herein Rio Negro lineage) and a second widespread throughout the remaining of the species' distribution (herein Amazonas lineage). These lineages occur over a very broad geographical range, suggesting that despite occurring in regions separated by thousands of kilometres, individuals of the distinct lineages fail to occupy each other's habitats, hundreds of metres apart and not separated by physical barrier. Reproductive isolation was assessed in isolated pairs exposed to black-water conditions. All pairs with at least one individual of the lineage not native to black waters showed significantly lower spawning success, suggesting that the water type affected the fitness and contributed to reproductive isolation. Our results endorse Wallace's intuition and highlight the importance of ecological factors in shaping diversity of the Amazon fish fauna.

A Late Cretaceous epeiric carbonate platform: the Haftoman Formation of Central Iran

An integrated study of the litho-, bio-, and microfacies of several sections has greatly improved the knowledge on the stratigraphy and depositional setting of the Coniacian to Campanian Haftoman Formation in the Khur area of the northern Yazd Block, Central Iran. Generally, the Haftoman Formation rests on a major tectonic unconformity and commences with a basal conglomerate followed by up to 900 m of shallow-water carbonates with local red sandstone intercalations. Five different depositional environments (from distal to proximal) characterize the facies associations (FA) of the Haftoman Formation: silty, spiculitic wackestone (proximal basin, FA I), bio-/intraclastic wacke-, pack-, and grainstone (marginal shoals, FA II), bioclastic rud-/float-/boundstone (outer platform, FA III), silty mud-/wackestone (lagoonal inner platform, FA IV), and sandstone/sandy limestone (areas close to the mouth of ephemeral streams, FA V). The litho-, micro-, and biofacies of the Haftoman Formation are typical for an epeiric carbonate platform characterized by an arid climate and lagoonal circulation, resulting in nutrient-poor waters, warm temperatures, and high salinities. The Haftoman Platform was attached to an emergent arid hinterland formed by the Anarak Metamorphic Complex to the west and southwest of the study area. Unconformity-bounded depositional units indicate sea-level changes that may correspond to 400-kyr high-frequency sequences but further studies are needed to fully exploit the potential of sequence stratigraphy for regional and inter-regional correlation of the Haftoman Formation.

Phytoplankton response to fish-induced environmental changes in a temperate shallow pond-type lake

AbstractSince 1967, the temperate, shallow, pond-type Lake Warniak has been subjected to different biomanipulation methods including the introduction of common carp,Cyprinus carpioL., grass carp,Ctenopharyngodon idella(Val.), silver carp,Hypophthalmichthys molitrix(Val.), and bighead carp,Hypophthalmichthys nobilis(Richardson) and then their removal in an effort to control macrophytes and phytoplankton. Recently, pilot stocking with predatory fish, particularly pike,Esox luciusL., has also been conducted. Hence, an examination of the long-term response patterns of phytoplankton to multiple fish-induced stressors was undertaken. In recent years,Charadomination (2000-2004) has helped to stabilize a clear-water state, high/good ecological status, and meso-eutrophic conditions. After the disappearance of Charales in 2004, the rapid, unstable changes in phytoplankton biomass, structure, and biodiversity suggested a shift toward a turbid-water state. As a result, the phytoplankton assemblages changed from those dominated by cryptophytes Y+X2+X1+LO(2000-2004) through those dominated by cyanobacteria K (2005-2008), dinoflagellates LO+Y (2009-2011), and cryptophytes Y+LO+F+X2 (2012), to those dominated by diatoms D+K+P+A (2013-2014) with representative taxa that occur in nutrient-rich and/or nutrient-poor water bodies. The 1967-2014 changes indicated that four periods, two with clear-water state and two with turbid-water state, alternately, one after the other, resulted from different fish pressure. Higher autochthonous fish biomass was usually accompanied by lower phytoplankton biomass. In contrast, the introduction of Cyprinidae fish had a stimulating effect on summer phytoplankton dominated by cyanobateria. Among the nutrients, only phosphorus played an important role.

The subpolar gyre regulates silicate concentrations in the North Atlantic

The North Atlantic is characterized by diatom-dominated spring blooms that results in significant transfer of carbon to higher trophic levels and the deep ocean. These blooms are terminated by limiting silicate concentrations in summer. Numerous regional studies have demonstrated phytoplankton community shifts to lightly-silicified diatoms and non-silicifying plankton at the onset of silicate limitation. However, to understand basin-scale patterns in ecosystem and climate dynamics, nutrient inventories must be examined over sufficient temporal and spatial scales. Here we show, from a new comprehensive compilation of data from the subpolar Atlantic Ocean, clear evidence of a marked pre-bloom silicate decline of 1.5–2 µM throughout the winter mixed layer during the last 25 years. This silicate decrease is primarily attributed to natural multi-decadal variability through decreased winter convection depths since the mid-1990s, a weakening and retraction of the subpolar gyre and an associated increased influence of nutrient-poor water of subtropical origin. Reduced Arctic silicate import and the projected hemispheric-scale climate change-induced weakening of vertical mixing may have acted to amplify the recent decline. These marked fluctuations in pre-bloom silicate inventories will likely have important consequences for the spatial and temporal extent of diatom blooms, thus impacting ecosystem productivity and ocean-atmosphere climate dynamics.

Paleoenvironmental changes and influence on Operculodinium centrocarpum during the Quaternary in the Campos Basin, southwestern Brazil

The purpose of this paper is to document the changes observed in the Quaternary dinoflagellate assemblages from 80 core samples from the Campos Basin. The Interglacial (Subzone X1), Glacial (Subzones Y5 to Y2), Last Glacial Maximum (Subzone Y1) and Post-Glacial (Zone Z) intervals were identified. High abundance of Operculodinium centrocarpum suggests the warm, high salinity and nutrient-poor water conditions dominated the upper water column of the Campos Basin. The climate and oceanic current dynamic of the continental slope of the Campos Basin appears to has been a significant controlling factor in the distribution of dinocysts, particularly of O. centrocarpum, during the Pleistocene/Holocene transition.

Wind-induced subduction at the South Atlantic subtropical front

The South Atlantic Subtropical Front, associated with the eastward-flowing South Atlantic Current, separates the colder, nutrient-rich waters of the subpolar gyre from the warmer, nutrient-poor waters of the subtropical gyre. Perturbations to the quasi-geostrophic, eastward flow generate meanders and filaments which induce cross-frontal exchange of water properties. Down-front winds transport denser waters from the South over warm waters from the North, inducing convective instability and subduction. Such processes occur over spatial scales of the order of 1 km and thus require high horizontal spatial resolution. In this modeling study, a high-resolution (4 km) regional grid is embedded in a basin-wide configuration (12 km) of the South Atlantic Ocean in order to test the importance of submesoscale processes in water mass subduction along the subtropical front. Stronger and more numerous eddies obtained in the high-resolution run yield more intense zonal jets along the frontal zone. Such stronger jets are more susceptible to instabilities, frontogenesis, and the generation of submesoscale meanders and filaments with $\mathcal {O}(1)$ Rossby number. As a consequence, vertical velocities larger than 100 md 1 are obtained in the high-resolution run, one order of magnitude larger than in the low-resolution run. Wind-driven subduction occurs along the frontal region, associated with negative Ertel potential vorticity in the surface layer. Such processes are not observed in the low-resolution run. A passive tracer experiment shows that waters with density characteristics similar to subtropical mode waters are preferentially subducted along the frontal region. The wind-driven buoyancy flux is shown to be much larger than thermal or haline fluxes during the wintertime, which highlights the importance of the frictional component in extracting PV from the surface ocean and inducing subduction, a process that has been overlooked in subtropical mode water formation in the region.

Long-term vegetation, climate and ocean dynamics inferred from a 73,500 years old marine sediment core (GeoB2107-3) off southern Brazil

Long-term changes in vegetation and climate of southern Brazil, as well as ocean dynamics of the adjacent South Atlantic, were studied by analyses of pollen, spores and organic-walled dinoflagellate cysts (dinocysts) in marine sediment core GeoB2107-3 collected offshore southern Brazil covering the last 73.5 cal kyr BP. The pollen record indicates that grasslands were much more frequent in the landscapes of southern Brazil during the last glacial period if compared to the late Holocene, reflecting relatively colder and/or less humid climatic conditions. Patches of forest occurred in the lowlands and probably also on the exposed continental shelf that was mainly covered by salt marshes. Interestingly, drought-susceptible Araucaria trees were frequent in the highlands (with a similar abundance as during the late Holocene) until 65 cal kyr BP, but were rare during the following glacial period. Atlantic rainforest was present in the northern lowlands of southern Brazil during the recorded last glacial period, but was strongly reduced from 38.5 until 13.0 cal kyr BP. The reduction was probably controlled by colder and/or less humid climatic conditions. Atlantic rainforest expanded to the south since the Lateglacial period, while Araucaria forests advanced in the highlands only during the late Holocene. Dinocysts data indicate that the Brazil Current (BC) with its warm, salty and nutrient-poor waters influenced the study area throughout the investigated period. However, variations in the proportion of dinocyst taxa indicating an eutrophic environment reflect the input of nutrients transported mainly by the Brazilian Coastal Current (BCC) and partly discharged by the Rio Itajaí (the major river closest to the core site). This was strongly related to changes in sea level. A stronger influence of the BCC with nutrient rich waters occurred during Marine Isotope Stage (MIS) 4 and in particular during the late MIS 3 and MIS 2 under low sea level. Evidence of Nothofagus pollen grains from the southern Andes during late MIS 3 and MIS 2 suggests an efficient transport by the southern westerlies and Argentinean rivers, then by the Malvinas Current and finally by the BCC to the study site. Major changes in the pollen/spore and dinocyst assemblages occur with similar pacing, indicating strongly interlinked continental and marine environmental changes. Proxy comparisons suggest that the changes were driven by similar overarching factors, of which the most important was orbital obliquity.

Comparing and contrasting flooded and unflooded forests in Western Amazonia: seed predation, seed pathogens, germination

Because of the importance of the Amazon to our shared human future and because we need to understand how its forests regenerate, I set out seeds for a week in igapó, palm, terra firme, várzea and white sand forests and then collected them, scoring seed losses to predators, seed losses to pathogens and seeds that germinated. I found (1) terra firme forest, white sand forest, várzea forest and igapó forest under water 1 month every year, were significantly different for seed mechanisms and tolerances, terra firme forest, palm forest, várzea forest and igapó forest under water 1 month per year, were significantly different among species, and the interaction term was significant for all forests except for the two most flooded igapó forests, (2) in terra firme forest seed predators took most seeds regardless of species, (3) in palm forest species were different regardless of seed mechanism and tolerance, (4) in white sand forest seed predators took most seeds regardless of species, (5) in várzea forest seed predators took most seeds but with some species differences and (6) in igapó forest under water 1 month per year, there were differences in predation, pathogens and germination, and in species variation. I conclude that seed predation losses strength as forests become more stressed either by loss of soil fertility or by flooding with nutrient-poor water. Conversely seed pathogens become more important with water-logged soils and with flooding. Seed loss variation among species within forests was always a secondary factor.

High rates and close diel coupling of primary production and ecosystem respiration in small, oligotrophic lakes

Studies on small, shallow lakes are few and have traditionally focused on humic lakes, whereas transparent, oligotrophic lakes dominated by submerged macrophytes have been overlooked. This may have given rise to a skewed perception of shallow lakes as being well mixed, turbid and dominated by ecosystem respiration relative to primary production. Mixing patterns and ecosystem metabolism in five oligotrophic shallow lakes dominated by charophytes were investigated in order to determine gross primary production, ecosystem respiration, their regulation and mutual coupling in this very common lake type. Although lakes were very shallow (<0.5 m), high charophyte biomass caused strong daytime stratification followed by nocturnal mixing. Despite the nutrient-poor water, volumetric rates of production and respiration during spring–summer were high compared to most medium to large lakes. This intensive metabolism is likely a result of the high charophyte biomass and the shallow mixed surface layer. Areal rates of production and respiration were also high compared to values from other aquatic systems. Strong coupling between daily rates of production and respiration suggested that the majority of organic substrates for ecosystem respiration were produced within the lakes. Net ecosystem production was slightly positive during the growth season. This study highlights the role of submerged macrophytes as primary drivers of temperature dynamics, stratification-mixing as well as high metabolism in small, shallow lakes with dense vegetation.

Net-phytoplankton communities in the Western Boundary Currents and their environmental correlations

This study investigated net-phytoplankton biomass, species composition, the phytoplankton abundance horizontal distribution, and the correlations between net-phytoplankton communities and mesoscale structure that were derived from the net samples taken from the Western Boundary Currents during summer, 2014. A total of 199 phytoplankton species belonging to 61 genera in four phyla were identified. The dominant species included Climacodium frauenfeldianum, Thalassiothrix longissima, Rhizosolenia styliformis var. styliformis, Pyrocystis noctiluca, Ceratium trichoceros, and Trichodesmium thiebautii. Four phytoplankton communities were divided by cluster analysis and the clusters were mainly associated with the North Equatorial Counter Current (NECC), the North Equatorial Current (NEC), the Subtropical Counter Current (STCC), and the Luzon Current (LC), respectively. The lowest phytoplankton cell abundance and the highest Trichodesmium filament abundance were recorded in the STCC region. The principal component analysis showed that T. thiebautii preferred warm and nutrient poor water. There was also an increase in phytoplankton abundance and biomass near 5°N in the NECC region, where they benefit from upwellings and eddies.

The trapping of organic matter within plant patches in the channels of the Okavango Delta: a matter of quality

The role of in-stream aquatic vegetation as ecosystem engineers in the distribution of organic matter was investigated in the Okavango Delta, one of the world’s largest oligotrophic wetlands. The Okavango channel beds are covered up to 50% with submerged macrophyte patches. By accumulating and concentrating organic matter in the sediments below the patches, macrophytes are likely able to locally forestall a deficiency of nutrients. Up to 21 times more N, 18 times more C, 13 times more P and 6 times more Si can be found in vegetated sediments compared to non-vegetated sediments. Nutrient specific accumulation relates to its relative scarcity in the overlaying water. There is a depletion of dissolved N relative to P, whereas Si is relatively abundant. The Okavango Delta water can generally be characterised as oligotrophic based on plant species composition (e.g. presence of carnivorous plants and absence of floating plants), low plant N:P ratios, and low nutrient- and element-concentrations. Local mineralization and intensified nutrient cycling in the sediments is hypothesized to be crucial for the macrophytes’ survival because it provides a key source of the essential nutrients which plants otherwise cannot obtain in sufficient quantities from the nutrient poor water. By engineering the ecosystem as such, channel vegetation also retards the loss of elements and nutrients to island groundwater flow, contributing to one of the key processes driving the high productivity of the Okavango Delta, making it unique among its kind.

A Trait-Based Model for Describing the Adaptive Dynamics of Coral-Algae Symbiosis

The survival of many ecological communities relies on the symbiotic relationships formed by various organisms. An example of a symbiotic association that is often described as mutualistic is the one between corals and algae. Since the algae are located within coral epidermis, they are referred to as endosymbiont (more generally symbiont) whereas the corals are referred to as host. This association is based on the exchange of photosynthetically fixed carbon from algae to corals and inorganic nutrients, acquired from animal waste metabolites or directly from seawater, from corals to algae. The evolution of this symbiotic relationship has enabled the emergence of highly productive and diverse coral reef ecosystems in nutrient-poor waters of the tropical oceans. Here we present an adaptive, trait-based model that describes the temporal dynamics of this association. Given that corals control the flux of inorganic nutrients to the algae, we focus on the adaptation of a hypothetical trait expressed by the coral population: investment of energy in the symbiotic relationship. Investment of energy produces losses for the corals that reflect costs for algal photosynthetic efficiency and for sustaining and maintaining the symbiont population. The fitness of the coral is modelled as the net benefit obtained by the symbiotic association. The model features a decrease in the fraction of energy invested by the corals with increasing symbiont to host biomass ratio. Our sensitivity analyses show that the best conditions for the survival of the simulated coral-algae community occur for a broad range of symbiont to host biomass ratio if the costs of symbiosis are low. With increasing costs, the survival region narrows down to a smaller range of symbiont to host biomass ratio. Finally, a break down of the symbiotic relationship and a consequent collapse of the coral-algae system occur under shock changes in algal abundance.

Diazotrophs: Overlooked Key Players within the Coral Symbiosis and Tropical Reef Ecosystems?

Coral reefs are highly productive ecosystems thriving in nutrient-poor waters. Their productivity depends largely on the availability of nitrogen, the proximate limiting nutrient for primary production. In reefs, the major nitrogen pathways include regeneration, nitrification, ammonification and dinitrogen (N2) fixation. N2 fixation is performed by prokaryotes called ‘diazotrophs’ that abound in coral rubbles, sandy bottoms, microbial mats or seagrass meadows. Corals, which are the main reef builders, have developed a partnership with dinoflagellates which transform dissolved inorganic nitrogen into amino acids and protein, and with diazotrophs to gain diazotrophically-derived nitrogen (DDN). Pioneering studies found active diazotrophic cyanobacteria in the corals’ mucus and/or tissue, and later high throughput sequencing efforts have described diverse communities of non-cyanobacterial diazotrophs associated with scleractinian corals. Yet, the metabolic processes behind these associations and how they benefit corals is currently not well understood. While genomic studies describe the diversity of diazotrophs and isotopic tracer experiments quantify N2 fixation rates, combined advanced methods are needed to elucidate the mechanisms behind the transfer of DDN to the coral holobiont and whether these mechanisms change according to the identity of the diazotrophs or coral species. Here we review our current knowledge on N2 fixation in corals: the diversity and localization of diazotrophs in the coral holobiont, the environmental factors controlling N2 fixation, the fate of DDN within the coral symbiosis as well as its potential role in coral resilience. We finally summarize the unknowns: are the diversity, abundance and localization of diazotrophs within the holobiont species- and/or site-specific? Do they have an impact on DDN production? What are the metabolic mechanisms implicated? Do they change spatially, temporally or according to environmental factors? We encourage scientists to undertake research efforts to tackle these questions in order to shed light on nitrogen cycling in reef ecosystems and to understand if coral-associated N2 fixation can improve coral’s resilience in the face of climate change.

A SURVEY OF ISOETES COROMANDELINA L. F. POPULATIONS IN TIRUNELVELI DISTRICT

The genus Isoetes is a cosmopolitan genus found around the world. The genus consists of aquatic or semi-aquatic plants needing water for survival. The distribution of Isoetes coromandelina L. f. in the freshwater ponds of Tirunelveli district was studied. The results of the survey show that the population of Isoetes coromandelina in Tirunelveli district are healthy and flourish wherever non-polluted, nutrient poor waters are available. Although there is no danger to the populations of Isoetes at present, water pollutioncould endanger the survival of the species.

Integrating ecological roles and trophic diversification on coral reefs: multiple lines of evidence identify parrotfishes as microphages

Coral reef ecosystems are remarkable for their high productivity in nutrient-poor waters. A high proportion of primary production is consumed by the dominant herbivore assemblage, teleost fishes, many of which are the product of recent and rapid diversification. Our review and synthesis of the trophodynamics of herbivorous reef fishes suggests that current models underestimate the level of resource partitioning, and thus trophic innovation, in this diverse assemblage. We examine several lines of evidence including feeding observations, trophic anatomy, and biochemical analyses of diet, tissue composition and digestive processes to show that the prevailing view (including explicit models) of parrotfishes as primary consumers of macroscopic algae is incompatible with available data. Instead, the data are consistent with the hypothesis that most parrotfishes are microphages that target cyanobacteria and other protein-rich autotrophic microorganisms that live on (epilithic) or within (endolithic) calcareous substrata, are epiphytic on algae or seagrasses, or endosymbiotic within sessile invertebrates. This novel view of parrotfish feeding biology provides a unified explanation for the apparently disparate range of feeding substrata used by parrotfishes, and integrates parrotfish nutrition with their ecological roles in reef bioerosion and sediment transport. Accelerated evolution in parrotfishes can now be explained as the result of (1) the ability to utilize a novel food resource for reef fishes, i.e. microscopic autotrophs; and (2) the partitioning of this resource by habitat and successional stage.

An unprecedented coastwide toxic algal bloom linked to anomalous ocean conditions.

A coastwide bloom of the toxigenic diatom Pseudo‐nitzschia in spring 2015 resulted in the largest recorded outbreak of the neurotoxin, domoic acid, along the North American west coast. Elevated toxins were measured in numerous stranded marine mammals and resulted in geographically extensive and prolonged closures of razor clam, rock crab, and Dungeness crab fisheries. We demonstrate that this outbreak was initiated by anomalously warm ocean conditions. Pseudo‐nitzschia australis thrived north of its typical range in the warm, nutrient‐poor water that spanned the northeast Pacific in early 2015. The seasonal transition to upwelling provided the nutrients necessary for a large‐scale bloom; a series of spring storms delivered the bloom to the coast. Laboratory and field experiments confirming maximum growth rates with elevated temperatures and enhanced toxin production with nutrient enrichment, together with a retrospective analysis of toxic events, demonstrate the potential for similarly devastating ecological and economic disruptions in the future.

Reproductive pattern of the freshwater prawn Pseudopalaemon bouvieri (Crustacea, Palaemonidae) from hypo-osmotic shallow lakes of Corrientes (Argentina)

ABSTRACTPseudopalaemon bouvieri undergoes complete abbreviated development. The reproductive cycle (proportion and size of the sexually mature population and juvenile recruitment), fecundity and egg size of this prawn were examined in three subtropical shallow lakes. The reproductive cycle was seasonal; gonadal maturation occurred during the winter, ovigerous females were abundant in the spring and breeding occurred at the end of spring. Females produced small numbers of eggs (9–55) of relatively large sizes (1.0–2.1 mm). The proportion of ovigerous females with respect to the total number of females, the fecundity and egg size differed among the lakes according to the trophic state of the environments. Pseudopalaemon bouvieri has a reproductive strategy similar to other Palaemonidae species that inhabit nutrient-poor inland waters.

Experimental study of clay-hydrocarbon interactions relevant to the biodegradation of the Deepwater Horizon oil from the Gulf of Mexico

Adding clay to marine oil pollution represents a promising approach to enhance bacterial hydrocarbon degradation in nutrient poor waters. In this study, three types of regionally available clays (Ca-bentonite, Fuller's Earth and kaolin) were tested to stimulate the biodegradation of source and weathered oil collected from the Deepwater Horizon spill. The weathered oil showed little biodegradation prior to experimentation and was extensively degraded by bacteria in the laboratory in a similar way as the alkane-rich source oil. For both oils, the addition of natural clay-flakes showed minor enhancement of oil biodegradation compared to the non-clay bearing control, but the clay-oil films did limit evaporation. Only alkanes of a molecular weight (MW) > 420 showed significant reduction by enhanced biodegradation following natural clay treatment. In contrast, all fertilized clay flakes showed major bacterial degradation of the oil, with a 6–10 times reduction in alkane content, and an up to 8 fold increase in the rate of O2 consumption. Compared to the control, such treatment showed particular reduction of longer chained alkanes (MW > 226). The application of natural and fertilized clay flakes also showed selective reduction of PAHs, mainly in the MW range of 200–300, but without significant change in the toxicity indices measured. These results imply that a large variety of clays may be used to boost oil biodegradation by aiding attachment of fertilizing nutrients to the oil.

The role of cellular signaling during bleaching in the sea anemone, Aiptasia pallida.

Corals are symbiotic with dinoflagellate algae. This symbiosis allows corals to thrive in the nutrient poor waters of the tropics. Coral beaching is the loss of the endosymbiont due to environmental stressors such oxygen loss, bacterial infections, and changes in salinity and temperature. The mechanisms underlying temperature-induced coral bleaching are not well understood; however, it is known the process of apoptosis (programmed cell death) is involved. We are investigating the signaling pathways that are involved in temperature-induced bleaching in sea anemone, Aiptasia pallida. We are focusing on two pathways, MAP Kinase (ERK) and PI3Kinase (AKT), known to be activated by various environmental stresses and also play a role in apoptosis. The pathways are activated when the proteins involved are phosphorylated. To investigate whether temperature-induced bleaching activates these pathways, the tropical sea anemone, Aiptasia pallida is heat shocked from 25º C to 30º C. After the stress, proteins are isolated from the anemones, separated by protein electrophoresis and the phosphorylation levels of ERK and AKT are determined by Western blotting. Results from these studies will enable us to determine the extent that the MAP Kinase (ERK) and PI3Kinase (AKT) pathways are involved in bleaching and begin to determine how these pathways are involved in the apoptosis that results from bleaching.