Jason M. Lenes

Red tides in the Gulf of Mexico: Where, when, and why?

[1] Independent data from the Gulf of Mexico are used to develop and test the hypothesis that the same sequence of physical and ecological events each year allows the toxic dinoflagellate Karenia brevis to become dominant. A phosphorus-rich nutrient supply initiates phytoplankton succession, once deposition events of Saharan iron-rich dust allow Trichodesmium blooms to utilize ubiquitous dissolved nitrogen gas within otherwise nitrogen-poor sea water. They and the co-occurring K. brevis are positioned within the bottom Ekman layers, as a consequence of their similar diel vertical migration patterns on the middle shelf. Upon onshore upwelling of these near-bottom seed populations to CDOM-rich surface waters of coastal regions, light-inhibition of the small red tide of ~1 ug chl l(-1) of ichthytoxic K. brevis is alleviated. Thence, dead fish serve as a supplementary nutrient source, yielding large, self-shaded red tides of ~10 ug chl l(-1). The source of phosphorus is mainly of fossil origin off west Florida, where past nutrient additions from the eutrophied Lake Okeechobee had minimal impact. In contrast, the P-sources are of mainly anthropogenic origin off Texas, since both the nutrient loadings of Mississippi River and the spatial extent of the downstream red tides have increased over the last 100 years. During the past century and particularly within the last decade, previously cryptic Karenia spp. have caused toxic red tides in similar coastal habitats of other western boundary currents off Japan, China, New Zealand, Australia, and South Africa, downstream of the Gobi, Simpson, Great Western, and Kalahari Deserts, in a global response to both desertification and eutrophication.

Developing a Smart Semantic Web With Linked Data and Models for Near-Real-Time Monitoring of Red Tides in the Eastern Gulf of Mexico

In recent decades, the technology used to detect and quantify harmful algal blooms (commonly known as red tides) and characterize their physicochemical environment has improved considerably. A remaining challenge is effective delivery of the information generated from these advances in a user-friendly way to a diverse group of stakeholders. Based on existing infrastructure, we establish a Web-based system for near-real-time tracking of red tides caused by the toxic dinoflagellate Karenia brevis, which annually threatens human and environmental health in the eastern Gulf of Mexico. The system integrates different data products through a custom-made Web interface. Specifically, three types of data products are fused: 1) near-real-time ocean color imagery tailored for red tide monitoring; 2) K. brevis cell abundance determined by sample analysis; and 3) ocean currents from a nested and validated numerical model. These products are integrated and made available to users in Keyhole Markup Language (KML) format, which can be navigated, interpreted, and overlaid with other products in Google Earth. This integration provides users with the current status of red tide occurrence (e.g., location, severity, and spatial extent) while presenting a simple way to estimate bloom trajectory, thus delivering an effective method for near-real-time tracking of red tides.

Offshore forcing on the “pressure point” of the West Florida Shelf: Anomalous upwelling and its influence on harmful algal blooms

Gulf of Mexico Loop Current (LC) interactions with the West Florida Shelf (WFS) slope play an important role in shelf ecology through the upwelling of new inorganic nutrients across the shelf break. This is particularly the case when the LC impinges upon the shelf slope in the southwest portion of the WFS near the Dry Tortugas. By contacting shallow water isobaths at this “pressure point” the LC forcing sets the entire shelf into motion. Characteristic patterns of LC interactions with the WFS and their occurrences are identified using unsupervised neural network, self-organizing map, from 23 years (1993–2015) of altimetry data. The duration of the occurrences of such LC patterns is used as an indicator of offshore forcing of anomalous upwelling. Consistency is found between the altimetry-derived offshore forcing and the occurrence and severity of WFS coastal blooms of the toxic dinoflagellate, Karenia brevis: years without major blooms tend to have prolonged LC contact at the “pressure point,” whereas years with major blooms tend not to have prolonged offshore forcing. Resetting the nutrient state of the shelf by the coastal ocean circulation in response to deep-ocean forcing demonstrates the importance of physical oceanography in shelf ecology. A satellite altimetry-derived seasonal predictor for major K. brevis blooms is also proposed.

Forecasting and Modeling of Harmful Algal Blooms in the Coastal Zone: A Prospectus

Applications of numerical models to predict and eventually manage the onset, duration, and consequences of toxic phytoplankton events of coastal ecosystems require knowledge of both the ecophysiological properties of the specific organisms and the biophysical processes, which allow them to accumulate large biomass, despite the presence of other competitors. Harmful algal blooms are not always just local events. Furthermore, independent in situ plankton data sets from the Gulf of Mexico (GOM) and Mediterranean Sea over six decades, together with adjunct satellite color data, other nitrogen isotope signals of plankton and sediments, extant circulation models, and phytoplankton biomarkers within sediment cores of this similar ecosystem, all confirm the complex western GOM eutrophied sequence of phytoplankton succession.