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Increased nutrient loading into estuaries causes the accumulation of algal biomass, and microbial degradation of this organic matter decreases oxygen levels and contributes towards hypoxia. A second, often overlooked consequence of microbial degradation of organic matter is the production of carbon dioxide (CO2) and a lowering of seawater pH. To assess the potential for acidification … Read more
Studies of estuarine eutrophication have tended to focus on systems with continually flowing rivers, while little is known about estuaries from semi-arid/arid regions. Here we report results from an assessment of water quality conditions in Baffin Bay, Texas, a shallow (2 fold higher than in three other Texas estuaries. In contrast, inorganic nitrogen (ammonium, nitrate) … Read more
We hypothesized that the grazing on phytoplankton by the microzooplankton community is size-dependent and, therefore, the top-down control on phytoplankton by microzooplankton community could be one possible mechanism explaining why small phytoplankton become less abundant than large phytoplankton in eutrophic waters. We tested this hypothesis using the dilution method to measure microzooplankton grazing rates and … Read more
While there is growing interest in understanding how marine life will respond to future ocean acidification, many coastal ecosystems currently experience intense acidification in response to upwelling, eutrophication, or riverine discharge. Such acidification can be inhibitory to calcifying animals, but less is known regarding how non-calcifying macroalgae may respond to elevated CO2. Here, we report … Read more
The Louisiana shelf, in the northern Gulf of Mexico, receives large amounts of freshwater and nutrients from the MississippiAtchafalaya river system. These river inputs contribute to widespread bottom-water hypoxia every summer. In this study, we use a physicalbiogeochemical model that explicitly simulates oxygen sources and sinks on the Louisiana shelf to identify the key mechanisms … Read more
The Louisiana shelf (LA shelf) in the northern Gulf of Mexico experiences hypoxic conditions every summer due to the combination of eutrophication and strong water column stratification. Here we use a three-dimensional circulation model coupled with a simple oxygen model to examine the physical controls on hypoxia generation on the LA shelf. The model assumes … Read more
We investigate distributions of dissolved oxygen over the Texas-Louisiana shelf using spatially highly resolved observations in combination with a regional circulation model with simple oxygen dynamics. The observations were collected using a towed, undulating CTD during the Mechanisms Controlling Hypoxia (MCH) program. Mid-water oxygen minimum layers (dissolved oxygen lower than 3.2 mL L?1) were detected … Read more
Ecosystem-based fisheries-management (EBFM) is increasingly used in the United States (U.S.), including in the Gulf of Mexico (GOM). Producing distribution maps for marine organisms is a critical step in the implementation of EBFM. In particular, distribution maps are important inputs for many spatially-explicit ecosystem models, such as OSMOSE models, as well as for biophysical models … Read more
Ecosystem-based fisheries management (EBFM) and ecosystem restoration are gaining momentum worldwide, including in U.S. waters of the Gulf of Mexico (GOM). Ecosystem models are valuable tools for informing EBFM and restoration activities. In this paper, we provide guidance and a roadmap for ecosystem modeling in the GOM region, with an emphasis on model development and … Read more
Conserving and restoring submerged aquatic vegetation (SAV) are key management goals for estuaries worldwide because SAV integrates many aspects of water quality and provides a wide range of ecosystem services. Management strategies are typically focused on aggregated abundance of several SAV species, because species cannot be easily distinguished in remotely sensed data. Human land use … Read more