Growth and form in the reef-building coral Montastrea annularis

The in-situ growth rate of the reef coral Montastrea annularis on a reef at Jamaica, W. Indies was determined for a 1-year period using Alizarin Red-S staining techniques. Growth rate is correlated with water depth and growth form. The flattened growth form of M. annularis allows for continued rapid increase in colony surface area at low light intensities. The geomorphology of Jamaican reefs may in part be controlled by the population ecology of M. annularis.     

Maintenance of living space by sweeper tentacles of Montastrea cavernosa,a caribbean reef coral

The reef-building coral Montastrea cavernosa Linnaeus possesses sweeper tentacles which have enlarged nematocyst batteries. Sweeper tentacles appear to be used in defense of the coral's living space and may successfully deter mesenterial filament attacks from the more aggressive coral M. annularis. M. cavernosa therefore possesses a specialized defensive strategy that has not been taken into account by present models describing spatial competition in coral reef ecosystems.     

Depth-dependent photoadaption by zooxanthellae of the reef coral Montastrea annularis

Zooxanthellae living in colonies of the Caribbean reef coral Montastrea annularis photoadapt to depth-dependent attenuation of submarine light. Studies carried out at Discovery Bay, Jamaica, show that in shallow-living coral colonies, the zooxanthellae appear photoadapted to function at high light intensities, and do poorly if transplanted to low light intensities; in contrast, zooxanthellae in deeper-living coral colonies can be damaged by high light intensities. The adaptation to decreasing light intensity and changing spectral quality appears to be accomplished by increasing the size of the photosynthetic unit (PSU), as opposed to increasing the number of PSU's per cell. Whole cell absorption increases with depth, partially offsetting the loss of light energy due to depth-dependent attenuation. Calculations of photosynthetically usable radiation, the light an alga is capable of absorbing in its own submarine habitat, suggest that the algae at different depths are optimizing rather than maximizing their ability to harvest submarine light energy.     

Time dependent sorption behavior of dinotefuran,imidacloprid and thiamethoxam

Dinetofuran (DNT), imidacloprid (IMD) and thiamethoxam (THM) are among the neonicotinoid insecticides widely used for managing insect pests of agricultural and veterinary importance. Environmental occurrence of neonicotinoid in post-application scenario poses unknown issues to human health and ecology. A sorption kinetic study provides much needed information on physico-chemical interaction of neonicotinoid with soil material. In this research study, time-dependent sorption behavior of DNT, IMD and THM in vineyard soil was studied. Sorption kinetics studies were conducted over a period of 96 hours with sampling duration varying from 0, 2, 4, 8, 12, 24, 60 and 96 hours. All three neonicotinoids exhibited very low sorption potential for the soil investigated. Overall percent sorption for all three neonicotinoids was below 20.04 ± 2.03% with highest percent sorption being observed for IMD followed by DNT and THM. All three neonicotinoids are highly soluble with solubility increasing with IMD < THM < DNT. Although, DNT has the highest solubility among all three neonicotinoids investigated, it exhibited higher percent sorption compared to THM, indicating factors other than solubility influenced the sorption kinetics. Low sorption potential of neonicotinoids indicates greater leaching potential with regard to groundwater and surface water contamination.     

Using Remote Sensing to Reassess the Mass Mortality of Diadema antillarum 1983–1984

Abstract: The 1983–1984 mass mortality of the sea urchin Diadema antillarum remains one of the most severe die-offs ever recorded in the Caribbean. Before 1983, the herbivore D. antillarum was pervasive on coral reefs in the region. Nine months after first detection of the mass mortality, 95% of the urchins had perished, and algal cover of coral increased between 100% and 250%. A water-borne pathogen was hypothesized as the causative agent, but it was never isolated. To date, surface current patterns have been used exclusively to explain both the cause and the distribution patterns of the mortality event. Using archived satellite images, we re-examined the water-borne pathogen hypothesis and investigated whether other mechanisms could also account for the dissemination pattern in some areas. In addition, archived satellite images were utilized to detect changes in coral reef reflectance. For infections in the Gulf of Mexico and Bermuda, satellite images confirm that surface currents are likely responsible for the distribution of the pathogen. For infections in the eastern Caribbean (Curacao, U.S. Virgin Islands, Barbados), however, another mechanism, possibly ballast water exchange, must be considered because the surface current and infection patterns do not coincide. Changes in coral reflectance were detectable from Landsat thermatic mapping data before and after the mass mortality and correspond to the change in algal cover. Results from our study demonstrate the potential of satellite images for use in determining connectivity between regions of the Caribbean and in detecting changes in coral reef cover.     

Landsat Thematic Mapper: Detection of Shifts in Community Composition of Coral Reefs

Abstract: We assembled a time series of 20 Landsat thematic mapper images from 1982 to 1996 for Key Largo, Florida, to ascertain whether satellite imagery can detect temporal changes in coral reef communities. Selected reef and control areas were examined for changes in brightness, spectral reflectance, band ratios, spatial texture, and temporal texture (  pixel-to-pixel change over time). We compared the data to known changes in the reef ecosystem of Carysfort Reef and terrestrial sample sites. Changes in image brightness and spectral-band ratios were suggestive of shifts from coral- to algal-dominated community structure, but the trends were not statistically significant. The spatial heterogeneity of the reef community decreased in the early 1980s at scales consistent with known ecological changes to the coral community on Carysfort Reef. An analysis of pixel-scale variation through time, termed temporal texture, revealed that the shallow reef areas are the most variable in regions of the reef that have experienced significant ecological decline. Thus, the process of reef degradation, which alters both the spatial patterning and variability of pixel brightness, can be identified in unclassified thematic mapper images.