The light requirements for growth and photosynthesis in seagrasses with emphasis on Texas estuaries : a literature survey

During the last 20 years, seagrass communities throughout the world have experienced decreased productivity and distribution. These declines have often been attributed to decreased water transparency as a result of turbidity or shading by epiphytic algae. Epiphytic shading is often an indication of nutrient enrichment caused by anthropogenic inputs. Although both epiphytes and turbidity occur as natural phenomena, human activities can exacerbate existing natural conditions with adverse effects on seagrass communities. The objectives of this study were (a) to review the existing literature and data available on the effect of natural and anthropogenic factors on the underwater light environment; (b) to examine the relationship between light and seagrass distribution and productivity; and (c) to make recommendations on how to protect seagrass habitats in Texas bays and estuaries. To meet these goals, we have examined the available literature, emphasizing the physiological response of seagrasses to light and temperature. By using data and observations collected on a variety of species from around the world we may be better able to define the light requirements of Texas seagrasses. A knowledge of the minimum annual light requirements for seagrass growth is necessary to maintain the current distribution of Texas species. This information will also be required in the development of a management plan that permits the expansion and establishment of new seagrass habitat.Submitted to United States Environmental Protection Agency, Region 6 ... Dallas, Tx31 July 1993Marine Scienc

Trophic dynamics in marine nearshore systems of the Alaskan high arctic

Thesis (Ph.D.) University of Alaska Fairbanks, 198

Assessment of Little Bay sediment and water quality in relation to indices of seagrass condition

We measured a variety of water column and sediment parameters in Little Bay and its major tributary, Tule Creek, over the period from May 2008 to June 2010 in relation to seagrass (Halodule wrightii) condition indices. These measurements were collected in an attempt to better understand the Little Bay system and the factors that have contributed to the decline of seagrass distribution in the Bay. Although the contracted period of study was for one year (ending March 2010), we present hydrographic data that was collected starting May 2008."Report submitted to: City of Rockport, Aransas County Navigation District, Town of Fulton.""Mission-Aransas National Estuarine Research Reserve"--Leaf i.Marine Scienc

An Arctic Kelp Community in the Alaskan Beaufort Sea

The discovery of the "Boulder Patch", an area of cobbles and boulders with attached kelp and invertebrate life, is reported from Stefansson Sound, near Prudhoe Bay, Alaska. Geophysical surveys using side-scan sonar and low-frequency recording fathometers reveal that cobbles and boulders occur in patches of various sizes and densities. Despite a seasonal influx of sediments, the Boulder Patch is a nondepositional environment. Physical disruption of cobbles and boulders by deep draft ice is minimal due to offshore islands and shoals which restrict the passage of large ice floes into Stefansson Sound. The apparent absence of similar concentrations of rocks with attached biota along the Alaskan Beaufort Sea coast is explained by the scarcity of rocks in areas protected from ice abrasion and with no net sediment deposition. In Stefansson Sound, the rocks provide a substratum for a diverse assortment of invertebrates and several species of algae. Recolonization by the biota was minimal on twelve boulders denuded and then left undisturbed for a three-year period. Sedimentation and grazing activity appear to be the major factors inhibiting recolonization. Linear growth in the kelp, Laminaria solidungula, is greatest in winter and early spring when nutrients are available for new tissue growth. The plant draws on stored food reserves to complete over 90% of its annual linear growth during the nine months of darkness under a turbid ice canopy. These reserves are accumulated by photosynthetic activity during the preceding summer. The total carbon contribution made by kelp in Steffansson Sound under these conditions is about 146 million g/yr or 7 g/m²/yr. A small percentage of this carbon is consumed directly by herbivores, but its importance to other organisms in not known and is under investigation.Key words: kelp, Laminaria solidungula, Flaxman boulders, Beaufort Sea, Boulder Patch, productivity, recolonization, geophysical surveys, side-scan sonar, lag depositsMots clés: varech, Laminaria solidungula, grosses pierres Flaxman, mer de Beaufort, Boulder Patch, productivité, recolonisation, levées géophysiques, sonar à balayage latéral, accumulations de pierres par déflatio

Community characterization of the Mission-Aransas National Estuarine Research Reserve and Surrounding Areas

The human dimensions of our environment greatly influence the effectiveness of coastal management. The human dimension is characterized by the social, cultural, economic, and political aspects of our surrounding environment. Changes to these aspects influence human perception and behaviors, which affect resource management decisions. An examination of the human dimension can provide a better understanding of not only resource flow, but also how human perception and behaviors are linked to resource flow. This knowledge can be used to develop decision support tools that will increase state and local managers' capacity to address the human dimensions of coastal management. The Mission-Aransas National Estuarine Research Reserve's (NERR) geographic, biophysical and political configurations are complex; therefore, a broad-scale assessment of the human dimension is necessary to provide a comprehensive snapshot of human behavior and trends. Characterization of the human dimension for the Mission-Aransas estuary and the surrounding watershed will document the current state of knowledge and provide a baseline assessment to identify changes in future characteristics of the human dimension. This characterization will support the Mission-Aransas NERR site profile development and management planning efforts. Characterization of the human dimension will also support development of a regional action strategy for applying social science to support ecosystem-based management and watershed planning in the Mission-Aransas NERR and the South Texas coast. Characterizations of the human dimension and development of a regional action strategy will benefit coastal resource management professionals within the Mission-Aransas NERR, the State of Texas, and the NERR System. The intent of this document is to create an approach that can be applied at other NERR sites to identify human dimension data gaps and applied social science approaches necessary to support NERR site profile development and long-term management and planning efforts. This information will be used to enhance the capacity for resource managers to make better coastal management decisions."April 5, 2007. Revised May 3, 2007."Marine Scienc

Spatial and temporal trends of the Western Arctic Ocean benthic community

Center for Water and the Environmen

Factors Controlling Seagrass Revegetation onto Dredged Material Deposits: A Case Study in Lower Laguna Madre, Texas

Our objective was to evaluate the influence of water quality and sediment chemistry on the survival and growth of Halodule wrightii transplanted onto unconsolidated dredged materials in Lower Laguna Madre, TX. Subsequent to transplanting activities, we measured environmental conditions and seagrass parameters at transplant and natural beds over a 1-yr period. Although water quality characteristics at the transplant and comparison sites were compatible with seagrass growth, transplants failed to survive for more than a few months. Seagrasses at natural sites received high light (\u3e6000 mols m−2 y−1) and exhibited typical patterns of annual growth, biomass and density as well as sediment chemical parameters. In contrast, the estimated annual quantum flux of 2500 to 3200 mols m−2 y−1 at the transplant sites was near the minimum light requirements for H. wrightii. The marginal light environment was a consequence of high turbidity from wind-driven sediment resuspension. Sediment erosion at the transplant site also resulted in a 30 cm increase in water depth. Sediment NH4 concentrations at the transplant sites were at or above the maximum values for Texas seagrasses (up to 600 µM). Although NH4 is generally considered a nutrient, recent evidence suggests that moderate to high NH4 concentrations can be toxic to below ground tissues. We hypothesize that substrate loss, chronic stress from elevated sediment NH4 levels coupled with minimal light caused the demise of the H. wrightii transplants. Consequently, this work illustrates the importance of site history and sediment bio-geochemistry as factors that control the success of seagrass transplanting efforts

Effects of dredge deposits on seagrasses : an integrative model for Laguna Madre : concluding report. Volume I, Executive Summary.

Interagency Coordination Team, U.S. Army Corps of Engineers, Galveston District, The University of Texas Marine Science Institute, Texas A&M University Department of Oceanography, Texas Parks and Wildlife DepartmentThis report presents the results of an interdisciplinary collaborative effort to develop an integrative model for seagrass productivity in Laguna Madre. One of the major components of this integrative model is the Laguna Madre Seagrass Model (LMSM) which was designed to interface with other component models described in this report, including carbon and nitrogen allocation, sediment diagenesis, and spectral irradiance and radiative transfer. Linkage with hydrodynamic and sediment transport models provided a potentially valuable management tool to assess the effects of maintenance dredging and resuspension of dredged material deposits on seagrasses of Laguna Madre.Texas A&M University and the U.S. Army Corps of Engineers (Galveston District) 96-PL-03Marine Scienc

Imprint of Climate Change on Pan-Arctic Marine Vegetation

The Arctic climate is changing rapidly. The warming and resultant longer open water periods suggest a potential for expansion of marine vegetation along the vast Arctic coastline. We compiled and reviewed the scattered time series on Arctic marine vegetation and explored trends for macroalgae and eelgrass (Zostera marina). We identified a total of 38 sites, distributed between Arctic coastal regions in Alaska, Canada, Greenland, Iceland, Norway/Svalbard, and Russia, having time series extending into the 21st Century. The majority of these exhibited increase in abundance, productivity or species richness, and/or expansion of geographical distribution limits, several time series showed no significant trend. Only four time series displayed a negative trend, largely due to urchin grazing or increased turbidity. Overall, the observations support with medium confidence (i.e., 5–8 in 10 chance of being correct, adopting the IPCC confidence scale) the prediction that macrophytes are expanding in the Arctic. Species distribution modeling was challenged by limited observations and lack of information on substrate, but suggested a current (2000–2017) potential pan-Arctic macroalgal distribution area of 820.000 km2 (145.000 km2 intertidal, 675.000 km2 subtidal), representing an increase of about 30% for subtidal- and 6% for intertidal macroalgae since 1940–1950, and associated polar migration rates averaging 18–23 km decade–1. Adjusting the potential macroalgal distribution area by the fraction of shores represented by cliffs halves the estimate (412,634 km2). Warming and reduced sea ice cover along the Arctic coastlines are expected to stimulate further expansion of marine vegetation from boreal latitudes. The changes likely affect the functioning of coastal Arctic ecosystems because of the vegetation’s roles as habitat, and for carbon and nutrient cycling and storage. We encourage a pan-Arctic science- and management agenda to incorporate marine vegetation into a coherent understanding of Arctic changes by quantifying distribution and status beyond the scattered studies now available to develop sustainable management strategies for these important ecosystems.publishedVersio

Kelp carbon sink potential decreases with warming due to accelerating decomposition

Cycling of organic carbon in the ocean has the potential to mitigate or exacerbate global climate change, but major questions remain about the environmental controls on organic carbon flux in the coastal zone. Here, we used a field experiment distributed across 28° of latitude, and the entire range of 2 dominant kelp species in the northern hemisphere, to measure decomposition rates of kelp detritus on the seafloor in relation to local environmental factors. Detritus decomposition in both species were strongly related to ocean temperature and initial carbon content, with higher rates of biomass loss at lower latitudes with warmer temperatures. Our experiment showed slow overall decomposition and turnover of kelp detritus and modeling of coastal residence times at our study sites revealed that a significant portion of this production can remain intact long enough to reach deep marine sinks. The results suggest that decomposition of these kelp species could accelerate with ocean warming and that low-latitude kelp forests could experience the greatest increase in remineralization with a 9% to 42% reduced potential for transport to long-term ocean sinks under short-term (RCP4.5) and long-term (RCP8.5) warming scenarios. However, slow decomposition at high latitudes, where kelp abundance is predicted to expand, indicates potential for increasing kelp-carbon sinks in cooler (northern) regions. Our findings reveal an important latitudinal gradient in coastal ecosystem function that provides an improved capacity to predict the implications of ocean warming on carbon cycling. Broad-scale patterns in organic carbon decomposition revealed here can be used to identify hotspots of carbon sequestration potential and resolve relationships between carbon cycling processes and ocean climate at a global scale.publishedVersio