Idiosyncratic Responses of Seagrass Phenolic Production Following Sea Urchin Grazing

While chemical defenses can determine plant persistence in terrestrial ecosystems and some marine macroalgae, their role in determining seagrass persistence in areas of intense grazing is unknown. As a first step toward determining if concentrations of feeding deterrents in seagrasses increase following herbivore attacks, we conducted 4 experiments using a common macrograzer (sea urchin Lytechinus variegatus) and 2 phylogenetically divergent seagrass species (Thalassia testudinum and Halodule wrightii). Macrograzer impacts on production of phenolic acids and condensed tannins varied somewhat idiosyncratically with season, urchin density, and distance from urchin damage. In general, phenolic concentrations were higher in both turtlegrass and shoalgrass in summer than in fall. Grazing led to increased condensed tannin concentrations in T. testudinum but had few effects on turtlegrass phenolic acid concentrations. Turtlegrass p-hydroxybenzoic acid concentrations increased locally in the grazed area and in areas \u3e2 cm above grazing. Similarly, condensed tannins in grazed H. wrightii leaves increased with urchin density in summer but decreased in fall while having few predictable effects on phenolic acid concentrations. Shoalgrass gallic acid concentrations increased in the lowest portions of grazed leaves. In choice feeding experiments in which urchins were offered agar food made with nighand low-phenolic seagrass tissue, high phenolic concentrations did not reduce urchin feeding, suggesting that the increases in phenolic concentrations we saw in turtlegrass and shoalgrass did not protect these plants against future sea urchin herbivory but rather some other factor, such as mesograzer feeding or pathogenic infection

Seagrass Deterrence to Mesograzer Herbivory: Evidence from Mesocosm Experiments and Feeding Preference Trials

Two laboratory experiments documented the effects of mesograzers (i.e. the gastropod Crepidula ustulatulina and the isopod Paracerceis caudata) on phenolic acid and condensed tannin production in 2 regionally abundant seagrasses—Thalassia testudinum (turtlegrass) and Halodule wrightii (shoalgrass). Subsequent paired choice experiments tested the hypothesis that phenolic acids and condensed tannins produced by these seagrasses deter mesograzer feeding. At the scale of the shoot, grazing by gastropods and isopods led to ~40 to 50% decreases in concentrations of some phenolic acids and ~20% decreases in condensed tannins in turtlegrass leaves. At a more refined spatial scale, concentrations of 2 of these compounds increased by 25 to 85% in areas near tissues damaged by C. ustulatulina and P. caudata in turtlegrass. In contrast, isopod feeding increased the concentrations of some shoalgrass phenolic acids by ~30 to 50%, while gastropod grazing led to ~25 to 50% higher concentrations of condensed tannins in shoalgrass leaves, suggesting that grazer identity and seagrass species play important roles in seagrass deterrent production. Amphipods (Batea catharinensis) consistently preferred agar food made from seagrass leaves with low phenolic concentrations in choice feeding experiments, indicating that phenolics can act as feeding deterrents to these mesograzers

Establishment of the Invasive Island Apple Snail Pomacea insularum (Gastropoda: Ampullaridae) and Eradication Efforts in Mobile, Alabama, USA

Species invasions are thought to be among the most detrimental of all anthropogenic disturbances. Invasive consumers severely impact native ecosystems through the consumption of and competition with native species. Worldwide, snails of the Family Ampullaridae have successfully colonized a wide range of habitats outside their native range. This is of great ecological concern because once established, these snails frequently exhibit rampant herbivory in the recipient ecosystem. Here, we chronicle the recent invasion of island apple snails (Pomacea insularum; d’Orbigny 1837) in a tributary of the Mobile–Tensaw Delta, Alabama, in order to establish a baseline against which future assessments of apple snail expansion can be measured. In addition, we discuss the current, albeit largely unsuccessful, efforts to eradicate these invaders post-invasion as well as the possible implications of the continued growth of this population should geographic expansion occur. We also provide the first genetic evidence, from the mitochondrial cytochrome c oxidase I (COI) sequence, positively identifying these snails as P. insularum. All individuals were identical for COI and genetically identical to invasive animals in Georgia and portions of Florida, as well as native animals near Buenos Aires, Argentina, indicating a possible secondary invasion from nearby invasive U.S. populations but, ultimately, an Argentinian origin. Based on our evidence, we suggest that the best control measures for apple snail invasions include increased proactive enforcement to prevent future invasions elsewhere in the southeastern United States (and similar areas), the adoption of research into new management strategies designed to prevent future invasions and slow the spread of established invasive populations, and rapid and overwhelming control and eradication efforts at the first sign of invasion

Use of Shallow Estuarine Habitats by Nekton in the Mobile-Tensaw River Delta, Alabama

We compared nekton density, composition, and biomass in fall 2009 and spring 2010 among three major habitat types (marsh, SAV=submerged aquatic vegetation dominated by Vallisneria americana, SNB=shallow nonvegetated bottom) commonly found throughout the Mobile-Tensaw River Delta (MTD) using 1-m2drop samplers. In the sampling design, habitat selection was based on vegetation composition. Sample locations (TR=Tensaw River, CB=Chocolatta Bay, and BC=Below Causeway) were selected based on their degree of tidal connectivity with the wider estuary (BC \u3e TR \u3e CB). Nekton distributional patterns varied among both locations and habitat types. Species richness was greater at BC than CB. The young of most estuarine-dependant fishery species (e.g., white shrimp, blue crab, gulf menhaden) were more abundant, and had more biomass, at BC and TR than CB. Estuarine residents (e.g., riverine grass shrimp, rainwater killifish) dominated the nekton in CB. Within locations, mean densities and biomass of abundant species were concentrated in vegetated (marsh, SAV) habitat types, and most species associated with vegetation structure were more abundant in SAV than marsh. Tidally unrestricted areas of the MTD may provide an important nursery for fishery species such as white shrimp, blue crab, gulf menhaden, and southern flounder. Additional studies will be needed to determine if these fishery species represent strong conduits for cross ecosystem transfer of energy and nutrients between the MTD and northern Gulf of Mexico

Economic Impact of Gulf of Mexico Ecosystem Goods and Services and Integration Into Restoration Decision-Making

Sustainability of natural resources requires balancing exploitation and conservation, enabled by management based on the best available scientific and economic information. Valuation of ecosystem goods and services is an important tool for prioritizing restoration efforts, recognizing the economic importance of conserving natural capital, and raising public awareness about the contribution of healthy ecosystems to social welfare, now and for future generations. The Deepwater Horizon oil spill (DHOS) in 2010 was a Gulf of Mexico ecological and economic disaster adding to decades-long degradation of the region’s coastal and marine environment. In 2010, revenues from provisioning ecosystem goods and services generated by the five U.S. states bordering the Gulf of Mexico contributed over $2 trillion per year to the nation’s gross domestic product, including$660 billion from the coastal county revenues and $110 billion from ocean revenues. Mexico and Cuba contribute at least another$40 billion per year from their Gulf coastal and ocean economies. Total economic value of Gulf ecosystem goods and services also requires valuation of nonmarket regulating, cultural, and supporting services, which are far more difficult to assess, but add billions more dollars per year. In light of this total economic value and trends in ecosystem stressors, new investment is necessary to ensure completeness, accuracy, and availability of Gulf economic impact data. Civil and criminal settlements related to the DHOS provide unprecedented opportunities for improving integration of ecosystem goods and services into decisions that affect Gulf restoration and sustainability. This paper highlights the economic contributions of Gulf ecosystem goods and services to the nation’s welfare, and recommends actions and investments required to ensure that they are valued, and integrated into decision-making

Prospects For Gulf of Mexico Environmental Recovery and Restoration

Previous oil spills provide clear evidence that ecosystem restoration efforts are challenging, and recovery can take decades. Similar to the Ixtoc 1 well blowout in 1979, the Deepwater Horizon (DWH) oil spill was enormous both in volume of oil spilled and duration, resulting in environmental impacts from the deep ocean to the Gulf of Mexico coastline. Data collected during the National Resource Damage Assessment showed significant damage to coastal areas (especially marshes), marine organisms, and deep-sea habitat. Previous spills have shown that disparate regions recover at different rates, with especially long-term effects in salt marshes and deepsea habitat. Environmental recovery and restoration in the northern Gulf of Mexico are dependent upon fundamental knowledge of ecosystem processes in the region. PostDWH research data provide a starting point for better understanding baselines and ecosystem processes. It is imperative to use the best science available to fully understand DWH environmental impacts and determine the appropriate means to ameliorate those impacts through restoration. Filling data gaps will be necessary to make better restoration decisions, and establishing new baselines will require long-term studies. Future research, especially via NOAA’s RESTORE Science Program and the state-based Centers of Excellence, should provide a path to understanding the potential for restoration and recovery of this vital marine ecosystem

Charge calibration of CsI(Tl)/photodiode spectroscopy systems

A charge calibration method for spectroscopy systems that use inorganic scintillators, photodiodes, and charge-sensitive preamplifiers is presented. The shaped square wave (SSW) method accounts for ballistic deficit when long decay time constants are present. The SSW method is demonstrated for CsI(T1) and compared to other calibration methods.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30115/1/0000491.pd