Digital library

Various types of floating algae have been reported in open oceans and coastal waters, yet accurate and timely detection of these relatively small surface features using traditional satellite data and algorithms has been difficult or even impossible due to lack of spatial resolution, coverage, revisit frequency, or due to inherent algorithm limitations. Here, a simple ocean color index, namely the Floating Algae Index (FAI), is developed and used to detect floating algae in open ocean environments using the medium-resolution (250- and 500- m) data from operational MODIS (Moderate Resolution Imaging Spectroradiometer) instruments. FAI is defined as the difference between reflectance at 859 nm (vegetation “red edge”) and a linear baseline between the red band (645 nm) and short-wave infrared band (1240 or 1640 nm). Through data comparison and model simulations, FAI has shown advantages over the traditional NDVI (Normalized Difference Vegetation Index) or EVI (Enhanced Vegetation Index) because FAI is less sensitive to changes in environmental and observing conditions (aerosol type and thickness, solar/viewing geometry, and sun glint) and can “see” through thin clouds. The baseline subtraction method provides a simple yet effective means for atmospheric correction, through which floating algae can be easily recognized and delineated in various ocean waters, including the North Atlantic Ocean, Gulf of Mexico, Yellow Sea, and East China Sea. Because similar spectral bands are available on many existing and planned satellite sensors such as Landsat TM/ETM+ and VIIRS (Visible Infrared Imager/Radiometer Suite), the FAI concept is extendable to establish a long-term record of these ecologically important ocean plants

Biogeochemical processes occurring near the sediment–water interface can play an important role in the establishment and persistence of hypoxic-to-anoxic conditions in areas of moderate-to-shallow water depth. Results are given in this paper for diagenetic modeling of two sites from the area on the Louisiana shelf west of the Mississippi River Delta known as the “dead zone”. This is one of the largest and most studied regions where seasonal coastal hypoxia occurs. The diagenetic model was capable of generating good matches with depth profiles at both sites in the upper 8 cm. Moderate differences between predicted and observed concentrations below this depth are most likely due to the highly non-steady state conditions in this region. The model was also able to predict extremely low dissolved sulfide concentrations and bacterial sulfate reduction rates that were in good agreement with independent direct observations. A sensitivity analysis of the model to input parameters showed that the model was much more sensitive to changes in values under hypoxic conditions than norm-oxic or anoxic conditions in the overlying water.

Simulations were carried out to first determine how the profiles of sediment porewater parameters and interfacial fluxes would change under differing quasi-steady state conditions where overlying dissolved oxygen concentrations and the rate of bioirrigation were varied. Next a non-steady state simulation was run to investigate how sediment biogeochemistry would change between these conditions during a hypothetical annual cycle. Results demonstrated a clear need to better understand the dynamic relationship among overlying water oxygen concentrations, the behavior of the benthic faunal community responsible for bioirrigation and sediment biogeochemistry.

Halophila decipiens Ostenfeld, a new record for the Hawaiian Islands, was collected from three locations spanning the archipelago: Midway Atoll at 3–15m deep, O’ahu Island at 1–2m deep, and Hawai’i Island at 40m deep. These findings expand the biogeographical distribution of this pantropical seagrass into the north central Pacific Ocean. Specimens showed morphological, reproductive and DNA characteristics typical of the species.

A new floristic index, [I/H]RCP, for the estimation of seaweed flora depending on the seawater temperature, is proposed. The index is a ratio of [I]to[H]. [I] is the number of species including both of species with alternation of isomorphic generations and without alternation of generations, and [H] is the number of species including species with alternation of heteromorphic generations, for Chlorophyta, Phaeophyta and Rhodophyta. This new floristic index, [I/H]RCP, clearly demonstrates the positive relationships with seawater temperature which effects the change of seaweed flora.