Nutrient enhanced coastal ocean productivity in the north Gulf of Mexico: understanding the effects of nutrients on a coastal ecosystem

The continental shelf adjacent to the Mississippi River is a highly productive system, often referred to as the fertile fisheries crescent. This productivity is attributed to the effects of the river, especially nutrient delivery. In the later decades of the 2oth century, though, changes in the system were becoming evident. Nutrient loads were seen to be increasing and reports of hypoxia were becoming more frequent. During most recent summers, a broad area (up to 20,000 krn2) of near bottom, inner shelf waters immediately west of the Mississippi River delta becomes hypoxic (dissolved oxygen concentrations less than 2 mgll). In 1990, the Coastal Ocean Program of the National Oceanic and Atmospheric Administration initiated the Nutrient Enhanced Coastal Ocean Productivity (NECOP) study of this area to test the hypothesis that anthropogenic nutrient addition to the coastal ocean has contributed to coastal eutrophication with a significant impact on water quality. Three major goals of the study were to determine the degree to which coastal productivity in the region is enhanced by terrestrial nutrient input, to determine the impact of enhanced productivity on water quality, and to determine the fate of fixed carbon and its impact on living marine resources. The study involved 49 federal and academic scientists from 14 institutions and cost $9.7 million. Field work proceeded from 1990 through 1993 and analysis through 1996, although some analyses continue to this day. The Mississippi River system delivers, on average, 19,000 m3/s of water to the northern Gulf of Mexico. The major flood of the river system occurs in spring following snow melt in the upper drainage basin. This water reaches the Gulf of Mexico through the Mississippi River birdfoot delta and through the delta of the Atchafalaya River. Much of this water flows westward along the coast as a highly stratified coastal current, the Louisiana Coastal Current, isolated from the bottom by a strong halocline and from mid-shelf waters by a strong salinity front. This stratification maintains dissolved and particulate matter from the rivers, as well as recycled material, in a well-defined flow over the inner shelf. It also inhibits the downward mixing of oxygenated surface waters from the surface layer to the near bottom waters. This highly stratified flow is readily identifiable by its surface turbidity, as it carries much of the fine material delivered with the river discharge and resuspended by nearshore wave activity. A second significant contribution to the turbidity of the surface waters is due to phytoplankton in these waters. This turbidity reduces the solar radiation penetrating to depth through the water column. These two aspects of the coastal current, isolation of the inner shelf surface waters and maintenance of a turbid surface layer, precondition the waters for the development of near bottom summer hypoxia.

Concurrent exposure of bottlenose dolphins (Tursiops truncatus) to multiple algal toxins in Sarasota Bay, Florida, USA

Sentinel species such as bottlenose dolphins (Tursiops truncatus) can be impacted by large-scale mortality events due to exposure to marine algal toxins. In the Sarasota Bay region (Gulf of Mexico, Florida, USA), the bottlenose dolphin population is frequently exposed to harmful algal blooms (HABs) of Karenia brevis and the neurotoxic brevetoxins (PbTx; BTX) produced by this dinoflagellate. Live dolphins sampled during capture-release health assessments performed in this region tested positive for two HAB toxins; brevetoxin and domoic acid (DA). Over a ten-year study period (2000–2009) we have determined that bottlenose dolphins are exposed to brevetoxin and/or DA on a nearly annual basis (i.e., DA: 2004, 2005, 2006, 2008, 2009; brevetoxin: 2000, 2004, 2005, 2008, 2009) with 36% of all animals testing positive for brevetoxin (n = 118) and 53% positive for DA (n = 83) with several individuals (14%) testing positive for both neurotoxins in at least one tissue/fluid. To date there have been no previously published reports of DA in southwestern Florida marine mammals, however the May 2008 health assessment coincided with a Pseudo-nitzschia pseudodelicatissima bloom that was the likely source of DA observed in seawater and live dolphin samples. Concurrently, both DA and brevetoxin were observed in common prey fish. Although no Pseudo-nitzschia bloom was identified the following year, DA was identified in seawater, fish, sediment, snails, and dolphins. DA concentrations in feces were positively correlated with hematologic parameters including an increase in total white blood cell (p = 0.001) and eosinophil (p<0.001) counts. Our findings demonstrate that dolphins within Sarasota Bay are commonly exposed to two algal toxins, and provide the impetus to further explore the potential long-term impacts on bottlenose dolphin health.

Status of water hyacinth infestation and control in River Kagera

During a regional workshop held in Mukono, Uganda (May 2001) by scientists and technocrats from Kenya, Tanzania and Uganda, working on water hyacinth management under the Lake Victoria Environmental Management Project (LVEMP), it was resolved that a survey of River Kagera be made to study the status of water hyacinth infestation and biological control in the river. Reports at the Mukono Workshop indicated that although Tanzania and Uganda had made serious effort to introduced biological control weevils (Neochefina eichhorniae and Neochetina brucht) on the weed in River Kagera, the level of establishment of biological control in the river was doubtful. Large quantities of water hyacinth biomass drifted down River Kagera into Lake Victoria daily. Similar reports of apparent inability of biological control weevils to fully establish and have effect on water hyacinth in River Nile, especially the Upper Victoria Nile, were also made by Uganda, and large quantities of weed biomass continuously drifted down the Upper Victoria Nile into Lake Kyoga. This was in spite of the successful control of the weed in Lake Victoria between 1998 and 2000

The rediscovery of Notopoides latus Henderson in the western Indian Ocean (Crustacea-Decapoda, Raninidae)

The small brachyuran family Raninidae Dana is represented in the Indo-West Pacific region by eight genera, with only some twenty species. One of the least known genera is Notopoides, which contains only a single species. This genus was first described by Henderson (1888) on the basis of material collected by H.M.S. "Challenger" from the Kei Islands, in the Banda sea off Indonesia. There have been no subsequent reports of this species in the ninety seven years since its original discovery. During the course of the study of the benthic fauna off the coast of East Africa, the Fisheries Research Vessel "Manihine" obtained five specimens of this rare species. These new records, collected during a short period of time, indicate that the species is probably not uncommon in this region, which also represents a great increase in its known geographical range. Specimens have been deposited in the collections of the National Museum, Nairobi, the Rijksmuseum van Natuurlijke Historie, Leiden, and the National Museum, Singapore: Catalogue numbers are crust. 1092 ; Crust. D. 28567; NMS. 1972.8.4.1, male of 35x26 respectively.