Technical Reports
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Item A Multivariate Statistical Analysis of Relationships Between Freshwater Inflows and Mollusk Distributions in Tidal Rivers in Southwest Florida(2006-12) Montagna, Paul A.The estuaries and rivers of the western coast of Florida, bordering the Gulf of Mexico, has been under intense study for some time with a goal to identify relationships between inflows, salinity, and natural resources. The mollusks have been show to be especially sensitive to salinity in many past studies, in many parts of the world. Several recent studied supported by the Southwest Florida Water Management District have focused on mollusk distributions for six tidal rivers: Peace River, Alafia River, Myakka River, Weeki Wachee River, Shell Creek, and the Shakett Creek Dona/Roberts Bay system. The purpose of the current project is to perform an inter-river, multivariate analysis that examines relationships between freshwater inflows, physicochemical variables that are affected by freshwater inflows (e.g. salinity, dissolved oxygen), and the distribution of mollusk populations in tidal rivers of southwest Florida. The design of all studies consists of mollusks being sampled along transects within each river system. The transects run lengthwise originating at the mouth of each river, heading upstream. To enable all of the rivers to be compared simultaneously, the measure of distance along each transect was standardized by grouping all stations along each transect into two-kilometer (2-km) segments. Community structure of mollusk species was analyzed using non-metric multi-dimensional scaling (MDS). Relationships between mollusk communities and environmental factors were identified by using a mulitvariate procedure that matches biotic (i.e., mollusc community structure) with environmental (i.e., sediments, temperature, dissolved oxygen, salinity and, pH) variables. Analyses were constrained to variables that were common to all data sets. In this limited analysis of southwest Florida mollusk communities, it is concluded that mollusk species are controlled more by water quality rather than the sediment they live in or on. The most important variable correlated with mollusk communities is salinity, which is a proxy for freshwater inflow. It is almost impossible to directly link community changes in response to inflow changes, because not replicates over time were carried out in the rivers sampled. Although total mollusk abundance was not a good indicator of inflow effects, certain indicator species have been identified however, that characterize salinity ranges in southwest Florida rivers. Corbicula fluminea, Rangia cuneata, and Neritina usnea were the only common species that occurred at salinities below 1 psu. Although, C. fluminea was the best indicator of freshwater habitat, because densities were highest below 2 psu, it is an introduced bivalve species. Rangia cuneata, a bivalve, has been noted as an indicator of a fresh- to brackish-water with an estimated tolerance of up to 20 psu in other studies as well. Neritina usnea is a gastropod and is also common in fresh- to brackish-water salinities. These salinity ranges may be useful in predicting mollusk community reactions to alterations in salinity that result from actual or simulated changes in freshwater inflow.Item Response of Benthic Organisms to External Conditions in Matagorda Bay(2006-12) Montagna, Paul A.; Coeckelenbergh, Cody; Evans, Anne D.The Lavaca-Colorado Estuary is a major estuarine system along the Texas coast that provides major economic benefit to the region by supporting a variety of agricultural, residential, industrial, and recreational functions. The Matagorda Bay Health Evaluation (MBHE) component of the LCRA/SAWS Water Project (LSWP) Study Plan was created to assess the environmental effects that could result from further changes to inflow patterns in the Matagorda Bay system. To support this assessment, a bio-energetic model, calibrated using a long-term data set of benthic biomass, was run to relate macrobenthic biomass to salinity within the estuary. This model was applied to the current study to assess the role of freshwater inflow in controlling benthic productivity. Benthic productivity was calculated for two groups of macrobenthos, suspension feeders and deposit feeders; in two bays, Lavaca Bay and Matagorda Bay. Simulations of the Lavaca-Colorado Estuary, based on a calibration of data from 1991 - 1996, fit the observed data relatively well. However, following the year 2000, simulations predicted a much higher benthic biomass than in observed data. The increase in benthic biomass is likely explained by the decrease in predator populations, particularly blue crabs, which reduced loss to predation. Simulations on deposit and suspension feeder biomass exhibited responses due to natural and simulated salinity changes in both bay systems. As salinity increased, deposit feeding biomass increased while suspension feeding biomass decreased. Total biomass in Lavaca Bay was found to increase as salinity increased, which indicates that reduced inflow rates in this bay would not harm the benthic community. Total biomass concentration in Matagorda Bay decreased initially with increasing salinity but then gradually increased. Thus, reducing the freshwater inflow may cause the upper river communities to take on downstream community appearance. This effect is probably due to the benthic community acclimating to the elevated salinity or more salt tolerant species populating the area. It is concluded that freshwater inflow plays an important role in maintaining the observed character of estuarine productivity through the combined effects of the frequency, duration, timing, and magnitude of inflow, particularly during droughts or low-flow periods.Item Characterization of Benthic Habitats in Proximity to The Lower Colorado River, Texas(2006-12) Montagna, Paul A.; Kalke, Richard; Palmer, Terence A.; Gossmann, AprilFreshwater inflow from the lower Colorado River supports a diverse ecological community in Matagorda Bay, East Matagorda Bay, and Oyster Lake. The region is part of the larger Lavaca-Colorado Estuary, which includes the adjacent Lavaca River and Lavaca Bay. The Lavaca-Colorado Estuary has been the subject of long-term benthic and water quality studies since 1988, but only six stations (two in Lavaca Bay and four in Matagorda Bay) have been sampled. The purpose of the current study is to sample over broader spatial scales in Matagorda Bay to determine how well the long-term stations characterize the spatial variability of benthic communities directly influenced by the Colorado River. Samples were collected from 18 stations to measure benthic community structure, hydrographic characteristics (depth, salinity, temperature, nutrients, and chlorophyll), and sediment characteristics (grain size, carbon and nitrogen content). Adjacent to the Colorado River, water quality and water column depth had higher correlations with macrobenthic community structure than sediment characteristics, but sediments were important overall. At a 40 % similarity level, macrobenthic communities were divided into five groups based on distance from the freshwater source, distance to the Gulf of Mexico, and bottom depth. Benthic communities in sheltered shallow habitats (< 0.5 m) were not represented by the current long-term stations, however all other community groups were represented. Apart from areas close to the Gulf Intracoastal Waterway and within 5 km of the Colorado River mouth, water quality in Matagorda Bay was well-characterized by the six long-term stations in low inflow conditions.Item Congo River Canyon Crossing Project, Benthic Analyses(2007-05) Montagna, Paul A.; Hyde, Larry J.Item The Effects of a Dredge Excavation Pit on Benthic Macrofauna in offshore Louisiana(2007-05) Montagna, Paul A.; Palmer, Terence A.Over two years after the original creation of a sand excavation pit 8 km off the Louisiana coast, benthic macrofauna communities and sedimentary characteristics are still effected. Macrofaunal communities inside the pit had lower abundance, biomass and diversity than communities outside the pit. This difference however, was only significant compared to some of the stations outside the pit. Results from multi-dimensional scaling and cluster analysis indicate that macrofaunal communities were less than 31 % similar inside the pit to communities outside the pit. The polychaete, Mediomastus ambiseta, was the most abundant species outside the excavation pit, but the species was only counted once inside the pit. The most dominant species, which made up over 90% of organisms inside the pit, was the pioneer polychaete, Paraprionospio pinnata. Three to five species were found at each station inside the pit as opposed to nine to 27 species at stations outside the pit. Differences in species compositions between inside and outside the pit were due to a loss of species rather than replacement by different species. All species inside the pit were also found outside the pit. Sediment inside the pit contained more silt and clay compared with outside, however no differences in water quality were detected. Sediment in the erosional zone outside the pit and on a dredge disposal mound was coarser than all other sediments sampled. Because the macrofaunal community inside the pit has not recovered within 38 months, it is likely that it will require more time before it resembles the surrounding conditions.Item Benthic Monitoring Project for The Mollie Beattie Coastal Habitat Community(2007-09) Montagna, Paul A.; Palmer, Terence A.Item Long-Term Response of Benthic Organisms to Freshwater Inflow in Texas Coastal Bend Estuaries(2007-10) Montagna, Paul A.The main difference between the Guadalupe and Lavaca-Colorado Estuaries relate to both size and Gulf exchange. Freshwater inflow has a larger impact on the smaller-restricted Guadalupe Estuary than in the Lavaca-Colorado. Both the smaller size and restricted inflow have synergistic effects, thus the Guadalupe is generally fresher and has higher carbon content than the Lavaca-Colorado. These conditions lead to higher benthic productivity in the Guadalupe Estuary. On the other hand, higher salinities and invasion of marine species is responsible for a more diverse community in Lavaca-Colorado Estuary. There is long-term, year-to-year variability in inflow. Higher inflow introduces higher values of dissolved inorganic nitrogen, which in turn stimulates primary production. The higher primary production, which is ephemeral and changes on very short time scales (days to weeks) drives benthic production, which changes over longer times scales (three to six months). Typically, nitrogen (which is derived from inflow and processed by estuarine organisms) is lost within the top 20 cm of sediment. Inflow also drives benthic community succession, due to different salinity tolerances of fresh, brackish, estuarine, and marine species. Due to the species changes and time scales of effects, the signal of inflow effects is easiest to measure and monitor using benthos as indicators. It is also apparent that long-term changes may be related to global climate cycles, e.g., El Niño events in the western Pacific Ocean. This study has benefitted by a statistical quirk (or trend) in climate data. There have been 11 El Niños in this century, three occurred in the first half and 8 have occurred in the second half. This short study (only 12 years) has captured three events. Because the long-term global cycles can vary from three to 20 years in length, long-term monitoring data will be required to develop reliable quantitative estimates of productivity versus inflow. Because the last few decades have been unusually wet, estimates based on the current study are likely to be over-estimates of the long-term average.Item Effect of Climatic Variability on Freshwater Inflow, Benthic Communities, and Secondary Production in Texas Lagoonal Estuaries: FY 2007(2008) Kim, Hae-Cheol; Montagna, Paul A.This is the final report for a 2-year project (TWDB contract numbers 07-483-0672 and 08-483-0791) with the objective to complete implementation of an ecological model to predict system-wide secondary production for two trophic groups of benthic organisms in response to different freshwater inflow regimes that result from the climatic ecotone along the Texas coast. The bioenergetic model was calibrated using an 11-year dataset (from 1988 to 1999) and validated with a 20-year data from (1988 to 2008) from four estuaries in South Texas: Lavaca-Colorado (LC), Guadalupe (GE), Nueces (NE) and Laguna Madre Estuaries (LM). The estuaries lie in a climatic gradient where LC and GE receive more rainfall than NE, and NE receives more rainfall than LM. Consequently inflow decreases along the gradient and salinity increases. In addition there is year-to-year variation in rain and inflow that results in wet and dry years. Therefore, this combination of the climatic gradient and temporal variability can be used to identify the effects of inflow on estuarine productivity. Among Texas estuaries, increased salinity (and thus decreased inflow) benefited deposit feeders, while suspension feeders were harmed, but the net overall effect is a decrease in functional diversity when salinity is increased. Within estuaries, the benthic community of secondary bays is harmed by reduced inflow, whereas, the community in primary bays appears to benefit in biomass increase by reduced inflow. This is because lower salinity regimes are required to support food production for suspension feeders, and there are more polyhaline deposit feeding species. Freshwater inflow is important in to maintain productivity and functional diversity; and required to maintain functional, healthy estuarine ecosystems.Item Effect of Freshwater Inflow on Macrobenthos Productivity in Minor Bay and River-Dominated Estuaries – Synthesis(2008-05) Montagna, Paul A.; Palmer, Terence A.; Pollack, Jennifer BeseresItem Colorado River Flow Relationships to Bay Health: Benthic Indicators - 2007(2008-05) Montagna, Paul A.Item McMurdo Station Long Term Monitoring - Biological and Toxicological Sampling, Analyses, and Data Synthesis - Phase 3(2008-09) Montagna, Paul A.; Palmer, Terence A.; Hyde, Larry J.Item Benthic Monitoring Project for The Mollie Beattie Coastal Habitat Community(2008-10) Montagna, Paul A.; Palmer, Terence A.Item Long-Term Response of Benthic Organisms to Freshwater Inflow in Texas Coastal Bend Estuaries(2008-10) Montagna, Paul A.The objective of this project was to use benthic infaunal invertebrates as bioindictors of ecosystem response to long-term changes in freshwater inflow to Texas bays. This objective was accomplished by collecting quarterly samples in five estuarine systems (the Lavaca-Colorado, Guadalupe, Mission-Aransas, Nueces, and Laguna Madre), analyzing archived samples; and relating benthic abundance, biomass, and diversity to freshwater inflow changes over time. A new indicator of freshwater inflow change was created using a multivariate analysis of water column characteristics (salinity, temperature, dissolved oxygen, pH, chlorophyll a, and nutrients). The main difference between the Guadalupe and Lavaca-Colorado Estuaries relate to both size and Gulf exchange. Freshwater inflow has a larger impact on the smaller-restricted Guadalupe Estuary than in the Lavaca-Colorado. Both the smaller size and restricted inflow have synergistic effects, thus the Guadalupe is generally fresher and has higher carbon content than the Lavaca-Colorado. These conditions lead to higher benthic productivity in the Guadalupe Estuary. On the other hand, higher salinities and invasion of marine species is responsible for a more diverse community in Lavaca-Colorado Estuary. There is long-term, year-to-year variability in inflow. Higher inflow introduces higher values of dissolved inorganic nitrogen, which in turn stimulates primary production. The higher primary production, which is ephemeral and changes on very short time scales (days to weeks) drives benthic production, which changes over longer times scales (three to six months). Typically, nitrogen (which is derived from inflow and processed by estuarine organisms) is lost within the top 20 cm of sediment. Inflow also drives benthic community succession, due to different salinity tolerances of fresh, brackish, estuarine, and marine species. Due to the species changes and time scales of effects, the signal of inflow effects is easiest to measure and monitor using benthos as indicators. It is also apparent that long-term changes may be related to global climate cycles, e.g., El Niño events in the western Pacific Ocean. This study has benefitted by a statistical quirk (or trend) in climate data. There have been 11 El Niños in this century, three occurred in the first half and 8 have occurred in the second half. This short study (only 12 years) has captured three events. Because the long-term global cycles can vary from three to 20 years in length, long-term monitoring data will be required to develop reliable quantitative estimates of productivity versus inflow. Because the last few decades have been unusually wet, estimates based on the current study are likely to be over-estimates of the long-term average.Item Observation Data Model (ODM) For Rincon Bayou, Nueces Delta(2009-01) Montagna, Paul A.; Nelson, KevinItem Colorado River Flow Relationships to Bay Health: Benthic Indicators – 2008(2009-04) Montagna, Paul A.Item Initial Meetings Summary - Habitat Management Plan of Corpus Christi/Nueces Bay(2009-05) Brenner, Jorge; Montagna, Paul A.; Pollack, Jennifer BeseresItem Workshop Summary: Habitat Management Plan for the Corpus Christi Bay Area(2009-06) Palmer, Terence A.; Brenner, Jorge; Nance, Thomas; Montagna, Paul A.Item Benthic monitoring of the Mollie Beattie Coastal Habitat community in relation to opening Packery Channel(2009-08) Montagna, Paul A.; Palmer, Terence A.Packery Channel was a natural channel that linked Corpus Christi Bay with the Gulf of Mexico, but has been closed since 1912. Construction to reopen the channel began in October 2003 and Packery Channel was reopened on 21 July 2005 by storm surge produced by Hurricane Emily. Official construction was completed in October 2006. A before versus after, control versus impact (BACI) design was implemented to assess the effects of reopening Packery Channel on water quality and estuarine macrofauna in Mollie Beattie Coastal Habitat Community (MBCHC), Corpus Christi Bay. Two deep (approximately 1 m below mean sea level) and two shallow (approximately 0.2 m below mean sea level) stations were sampled monthly for physical and biological characteristics at both control and impact sites between November and March from 2003 through 2009. There was little initial impact on the macrofaunal community composition, abundance, biomass, or N1 diversity caused by opening Packery Channel between July and December 2005. There was more difference in community composition between deep and shallow stations than between either before and after, or control and impact sites. Salinity was reduced at MBCHC and fluctuated in a diurnal pattern after the opening of Packery Channel, which is related to increased tidal exchange with the Gulf of Mexico. Packery Channel may have affected the salinity of MBCHC by introducing a diurnal fluctuation when water levels are high and by possibly decreasing the magnitude of long-term salinity fluctuations in MBCHC. The same salinity changes were not observed at reference site. Flow decreases along a gradient moving up Packery Channel away from the Gulf of Mexico, which indicates that tidal flows spill into MBCHC. Macrofauna diversity and biomass significantly decreased in the deep MBCHC site, but not in the reference site since Packery Channel opened. Macrofauna abundance increased in the deep MBCHC relative to the reference site in the second two-year period after the channel opened. Overall, the channel opening did not coincide with any changes in macrofauna abundance or diversity of the shallow MBCHC. Biomass did decrease in the shallow MBCHC after the opening of Packery Channel, but biomass is still greater than in the shallow reference site. The small change in hydrography in MBCHC has had little initial impact on macrobenthic communities, probably because MBCHC was already functioning as marine in terms of salinity.Item Boundary Map Report - Habitat Management Plan of Corpus Christi Bay(2009-08) Brenner, Jorge; Montagna, Paul A.; Nance, Thomas; Palmer, Terence A.Item Preliminary Habitat Management Plan for the Corpus Christi Bay Area(2009-09) Montagna, Paul A.