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The antipredatory chemical ecology of Caribbean reef sponges has been well studied, with two distinct ecological strategies described: chemically defended species use secondary metabolites to deter fish predators, while palatable species lack chemical defenses, but grow, reproduce, or recruit fast enough to persist despite predation. While most palatable sponge species are consistently undefended from fish predators in laboratory feeding assays, there are some species that exhibit individual inter- and intra-site variation ranging from palatable to defended. The objective of this study was to better document the extent of chemical defense variability for 7 of these species over a wider geographic range and to test the dual hypotheses that variably defended sponge species would be (1) more palatable, and (2) exhibit greater variability in chemical defenses from reefs without sponge predators than from reefs where predators are abundant. Laboratory feeding assays using the bluehead wrasse confirmed intraspecific variability of chemical defenses for Clathria virgultosa , Cribrochalina vasculum , Desmapsamma anchorata , Dragmacidon reticulata , Iotrochota birotulata , Niphates digitalis , and Xestospongia muta for sites across the Caribbean. Surprisingly, logistic regression models relating levels of sponge chemical defense to a site-specific index of spongivorous fish abundance offered little support for the hypothesis that predator abundance alters palatability for any of these variably defended sponge species. The presence of symbiotic zoanthids in the tissue of I. birotulata and N. digitalis did not alter palatability. While the selective effect of predation has segregated most species of Caribbean reef sponges into chemically defended and undefended categories, this study concludes that the situation is more complex for variably defended sponge species, and suggests that automimicry is a possible explanation for this alternative strategy. [ABSTRACT FROM AUTHOR]

Abstract: Chemical and physical defenses of sessile organisms against consumers are well described for both terrestrial and marine systems. However, previous studies have focused on chemical or physical defenses in isolation, and have not considered their interaction. Marine sponges provide a model system for testing this interaction. Some sponge species produce secondary metabolites that deter predation; they may also contain siliceous spicules, but previous studies have provided little evidence that spicules in isolation offer any defense against generalist fish predators. To determine whether the two components have an additive, antagonistic, or synergistic interaction, crude organic extracts and spicules from individuals of 8 Caribbean sponge species were isolated and tested in laboratory feeding assays. These included one chemically defended reef sponge (Agelas clathrodes) and seven known to be intermediately deterrent: six from reef habitats (Cinachyrella alloclada, Clathria virgultosa, Cribrochalina infundibulum, Niphates digitalis, Svenzea zeai, and Xestospongia muta) and one from mangrove habitats (Tedania ignis). Extracts and spicules were assayed at various concentrations, both individually and in combination, in laboratory feeding assays with the bluehead wrasse, Thalassoma bifasciatum. A SAS based GENMOD procedure based on an isobolographic analysis model was used for statistical comparisons. Four sponges (A. clathrodes, C. alloclada, C. virgultosa, and one of three individuals of X. muta) showed evidence of synergisms. Of these, synergy in C. alloclada, C. virgultosa, and X. muta was caused by approximately natural concentrations of extracts and spicules. The extract of A. clathrodes was deterrent, but combination assays required nearly a 3-fold reduction in extract concentration and an 8-fold increase in spicule concentration to show the synergistic effect. Contrary to previous findings, spicules from C. infundibulum and two of three individuals of X. muta were deterrent at natural concentrations. Sponge spicules may be defensive in isolation, or may enhance chemical defenses against consumers, but the lack of synergisms for individuals in 4 of 7 species with intermediate levels of chemical defense suggests that defensive synergy is not the general rule and, when present, may be an example of an exaptation. [Copyright &y& Elsevier]

The giant barrel sponge Xestospongia muta is now the dominant habitat-forming organism on many Caribbean coral reefs and has been observed to undergo cycles of bleaching similar to those seen for reef-building corals. We examined bleaching of X. muta at 15-m, 20-m, and 30-m depths over 2000-2005 on Conch Reef, Key Largo, Florida, to determine the spatial and temporal patterns of bleaching, whether bleaching affected sponge mortality, and whether there was a relationship between bleaching and seawater temperatures. Bleaching increased significantly with depth and was greater in autumn than spring, but the response was not uniform across the sponge population. Bleaching of X. muta did not result in sponge mortality, corroborating the conclusion that cyanobacterial symbionts of the sponge provide little or no benefit to the host. There was greater sponge bleaching with higher minimum daily seawater temperature anomalies within 30 d of surveys in the spring. For both the spring and autumn, there was greater bleaching with a higher number of positive 0.5°C daily anomalies within 14 d before surveys. Anomalously warm seawater temperatures fail to completely explain the variability of the observed bleaching response, however, and additional work would be required to conclusively determine whether a causal relationship between bleaching and temperature exists. As has been described for corals, bleaching of X. muta is likely a complex response that may be affected by multiple factors, including light availability and differences in bleaching susceptibility among Synechococcus symbionts. [ABSTRACT FROM AUTHOR]

Florida manatees (Trichechus manatus latiros-tris) are known to range north into the U.S. mid-Atlantic during warmer summer and fall months. However, rapid cooling of water temperatures in the fall can be detrimental to their survival in this region. This study reports upon all known mana-tee sightings (n = 211) and strandings (n = 9) from 1991 to 2012 in North Carolina and Virginia. The goals were to describe spatial and temporal patterns of manatee habitat use and mortality and relate those patterns to seasonal water temperatures, and to develop a finer-scale understanding of environmental temperatures across the region by deploying temperature data loggers at multiple sites throughout inland and coastal waterways. Although sightings were opportunistically gathered and, thus, not corrected for effort, they reveal a consistent picture of manatee presence in the mid-Atlantic. In both states, sightings were most common from June to October when water temperatures were above 20° C. Sightings in North Carolina were most common in the Intracoastal Waterway (27%), and in rivers and creeks (46%) in Virginia. Fine-scale temperature data collected throughout the region demonstrated highly variable, declining water temperatures in late fall, with temperatures dropping by as much as 1.35° C/d. Manatee sightings decreased precipitously with water temperature in November, while strandings increased. The results of this study demonstrate that manatees are predictably found in North Carolina and Virginia throughout the late spring, summer, and fall. These data can be used to plan future education and outreach, monitoring, regulatory actions, and habitat protection measures for this endangered species in this region. [ABSTRACT FROM AUTHOR]

Benthic microalgal biomass was measured as sediment chlorophyll a at two open ocean beaches in southeastern North Carolina between December 2003 and December 2004, spanning beach renourishment projects in spring 2004 at both beaches. Sampling design included replicate sampling (n = 6) at three elevations in the surf zone along paired transects at paired renourished and unnourished (control) sites at each beach 17 times during the study period. Grain-size analyses of beach sediments and measurements of water temperature were also conducted. Sediment grain size, expressed as mean grain size and percentage of total sediments <500 pm diameter, significantly affected sediment chlorophyll a values. Renourishment drove a small and temporary but significant increase in sediment chlorophyll a at one beach, which was interpreted as an effect of source material but otherwise had no detectable negative effects. The grain-size effects reinforce the importance of efforts to match material used for renourishment with existing beach sediments because benthic microalgae likely form a significant portion of the base of the food chain in surf-zone communities. [ABSTRACT FROM AUTHOR]

We examined the possibility that parameters of bottlenose dolphin signature whistles may serve as indicators of stress. Bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida, were recorded during brief capture-release events, which are potentially a source of short-term stress to these dolphins, although no effects of chronic or long-term stress have been observed over the 37+-year duration of the research. Whistles recorded during both brief capture-release and undisturbed, free-ranging conditions were examined to determine whether whistle parameters differ during capture-release versus undisturbed conditions; at the beginning of a capture-release session versus at the end of a session; during an individual's 1st capture-release session versus later capture-release sessions; and when a mother is caught and released with a dependent calf versus without a dependent calf (i.e., she has no dependent calf at the time of capture-release). We examined a variety of acoustic parameters, including whistle rate, number of loops (repetitive elements), maximum and minimum frequency, and loop, interloop, and whistle duration. We found that whistle rate and number of loops were greater during brief capture-release events than during undisturbed conditions; number of loops decreased and loop duration increased over the duration of a capture-release session; whistle rates decreased with number of capture-release sessions; and females caught and released with dependent calves produced whistles with higher maximum frequencies and shorter interloop intervals than when they did not have dependent calves. Thus, whistles appear to have potential as noninvasive indicators of stress in bottlenose dolphins. Further research is warranted in this area, for example by correlating physiological indices to whistle rates under varying levels of stress. Reliable, noninvasive correlates of stress could be used to monitor dolphins in a variety of circumstances, such as during exposure to anthropogenic noise. [ABSTRACT FROM AUTHOR]

Abstract: When using pulse-amplitude modulated (PAM) fluorometry to measure landscape-scale photosynthetic characteristics, diurnal variations in fluorescence during sampling may confound the assessment of the physiological condition. In this study, two photophysiological assessment techniques: Diurnal Yield and Diurnal Rapid Light Curve (RLC) were investigated in an attempt to incorporate the temporal and spatial scales of sampling into a physiological assessment of Thalassia testudinum in Florida Bay. Photosynthesis–irradiance (P–E) curves were calculated using both methods and the ability of each to predict the relationship between relative electron transport rates and irradiance was assessed. Both methods had limitations in providing consistent estimates of photosynthetic efficiency or capacity. The Diurnal Yield method produced unrealistically high predictions of photosynthetic capacity (relative electron transport rate (rETRmax), 417–1715) and saturation irradiance (I k, 1045–4681μmolphotonsm−2 s−1). In contrast, the Diurnal RLC method generally produced predictions of rETRmax (100–200) and I k (300–500μmolphotonsm−2 s−1) which were similar to average values calculated from each day''s RLCs. The Diurnal RLC method was unable to predict photosynthetic efficiency (α) only when ambient irradiances were continuously >I k during the sampling period. We believe that with sampling modifications in high-light or shallow environments, such as starting sampling earlier in the morning, extending sampling later in the day, or using the average α from each day''s RLCs, that the Diurnal RLC method can produce representative estimates of rETRmax, α, and I k, providing a method to characterize seagrass photosynthesis at the landscape-level. The Diurnal RLC method does not negate Diurnal variation but it produces a curve that incorporates the changing ambient light environment into the assessment of seagrass physiological status. [Copyright &y& Elsevier]

A comparative analysis, by expression profiling of maize, was performed to identify novel components in the mechanisms of maize responses to UV-B. Five high-altitude landraces grown from 2000 to 3400 m naturally receive higher UV-B fluence than plants at lower altitudes and similar latitudes. These high-altitude landraces were compared directly with a low-altitude line and with literature reports for other temperate maize lines. A microarray analysis demonstrated that among the UV-B responsive transcripts, several types of gene implicated in chromatin remodeling are differentially expressed before and after UV-B treatment in high-altitude lines. RNAi transgenic plants with lower expression of four such chromatin-associated genes exhibited hypersensitivity to UV-B by measurements of leaf arching, increased leaf chlorosis and necrosis, and altered UV-B regulation of selected genes. These results collectively suggest that genes involved in chromatin remodeling are crucial for UV-B acclimation and that some high-altitude lines exhibit adaptations to this challenge. [ABSTRACT FROM AUTHOR]

In Atlantic bottlenose dolphins Tursiops truncatus, both the thickness and lipid content of blubber vary across 0ntogeny and across individuals of differing reproductive and nutritional status. This study investigates how these changes in blubber morphology and composition influence its thermal properties. Thermal conductivity (W m-1 deg.-1, where deg. is °C) and thermal insulation (m² deg. W-1) of dolphin blubber were measured in individuals across an ontogenetic series (fetus through adult, N=36), pregnant females (N=4) and emaciated animals (N=5). These thermal properties were determined by the simultaneous use of two common experimental approaches, the heat flux disc method and the standard material method. Thickness, lipid and water content were measured for each blubber sample. Thermal conductivity and insulation varied significantly across ontogeny. Blubber from fetuses through sub-adults was less conductive (range=0.11–0.13±0.02 W m-1 deg.-1) than that of adults (mean=0.18 W m-1 deg.-1). The conductivity of blubber from pregnant females was similar to non-adult categories, while that of emaciated animals was significantly higher (0.24 ± 0.04 W m deg.-1) than all other categories. Blubber from sub-adults and pregnant females had the highest insulation values while fetuses and emaciated animals had the lowest. In nutritionally dependant life history categories, changes in blubber's thermal insulation were characterized by stable blubber quality (i.e. conductivity) and increased blubber quantity (i.e. thickness). In nutritionally independent animals, blubber quantity remained stable while blubber quality varied. A final, unexpected observation was that heat flux measurements at the deep blubber surface were significantly higher than that at the superficial surface, a pattern not observed in control materials. This apparent ability to absorb heat, coupled with blubber's fatty acid composition, suggest that dolphin integument may function as a phase change material. [ABSTRACT FROM AUTHOR]

This study investigated patterns of heat loss in bottlenose dolphins ( Tursiops truncatus) resident to Sarasota Bay, FL, USA, where water temperatures vary seasonally from 11 to 33°C. Simultaneous measurements of heat flux (HF) and skin surface temperature were collected at the body wall and appendages of dolphins during health-monitoring events in summer (June 2002–2004) and winter (February 2003–2005). Integument thickness was measured and whole body conductance (W/m2 °C) was estimated using HF and colonic temperature measurements. Across seasons, HF values were similar at the appendages, but their distribution differed significantly at the flipper and fluke. In summer, these appendages displayed uniformly high values, while in winter they most frequently displayed very low HF values with a few high HF values. In winter, blubber thickness was significantly greater and estimated conductance significantly lower, than in summer. These results suggest that dolphins attempt to conserve heat in winter. In winter, though, HF values across the body wall were similar to (flank) or greater than (caudal keel) summer values. It is likely that higher winter HF values are due to the steep temperature gradient between the body core and colder winter water, which may limit the dolphin’s ability to decrease heat loss across the body wall. [ABSTRACT FROM AUTHOR]