The Transition Zone Hypothesis on biodiversity of the Indian River Lagoon System, Florida

/ The Indian River Lagoon (IRL) system that extends from Ponce DeLeon Inlet to Jupiter Inlet is comprised of three interconnected estuarine lagoons: the Mosquito Lagoon (ML), the Banana River Lagoon (BRL), and the Indian River Lagoon (subdivided into North Indian River Lagoon, NIRL and the South Indian River Lagoon, SIRL). The declines in both the areal coverage and species diversity of seagrass communities within the IRL system are believed to be due in part to continued degradation of water quality. Large inflows of phosphorus (P) and nitrogen (N) -laden storm-water from urban areas and agricultural land have been correlated with higher chlorophyll a production in the central, south central, and the south segments of the lagoon. In a system as large and complex as the lagoon, N and P limitations are potentially subject to significant spatial and temporal variability. Total Kjeldahl nitrogen (TN) was higher in the north (1.25 mg/liter) and lower in the south (0.89 mg/liter). The reverse pattern was observed for total P (TP), i.e., lowest in the north (0.03 mg/liter) and highest at the south (0.14 mg/liter) ends of the IRL. This increased P concentration in the SIRL appears to have a significantly large effect on chlorophyll a production compared with the other segments, as indicated by stepwise regression statistics. This relationship can be expressed as follows: South IRL [chlorophyll a] = -8.52 + 162.41 [orthophosphate] + 7.86 [total nitrogen] + 0.38 [turbidity]; R(2) = 0.98**.

Seagrasses create foundational habitats in coastal ecosystems. One contributing factor to their global decline is disease, primarily caused by parasites in the genus Labyrinthula. To explore the relationship between seagrass and Labyrinthula spp. diversity in coastal waters, we examined the diversity and microhabitat association of Labyrinthula spp. in 2 inlets on Florida's Atlantic Coast, the Indian River Lagoon (IRL) and Banana River. We used amplicon-based high throughput sequencing with 2 newly designed primers to amplify Labyrinthula spp. from 5 seagrass species, water, and sediments to determine their spatial distribution and microhabitat associations. The SSU primer set identified 12 Labyrinthula zero-radius operational taxonomic units (ZOTUs), corresponding to at least 8 putative species. The ITS1 primer set identified 2 ZOTUs, corresponding to at least 2 putative species. Based on our phylogenetic analyses, which include sequences from previous studies that assigned seagrass-related pathogenicity to Labyrinthula clades, all but one of the ZOTUs that we recovered with the SSU primers were from non-pathogenic species, while the 2 ZOTUs recovered with the ITS1 primers were from pathogenic species. Some of the ZOTUs were widespread across the sampling sites and microhabitats (e.g. SSU ZOTU_10), and most were present in more than one site. Our results demonstrate that targeted metabarcoding is a useful tool for examining the relationships between seagrass and Labyrinthula diversity in coastal waters.

Plant traits mirror both evolutionary and environmental filtering process with universal trait-trait relationships across plant groups. However, plants also develop unique traits precisely to different habitats, inducing deviations of the trait coupling relations. In this study, we aimed to compare the differences in leaf traits and examine the generality and shifts of trait-trait relationships between alpine aquatic and terrestrial herbaceous plants on the Tibetan Plateau, to explore the precise adaptive strategies of aquatic and terrestrial plants for its habitats. We measured mass-based and area-based leaf N and P concentrations, N:P ratios and specific leaf area (SLA) of aquatic and terrestrial herbaceous plants. Standardized major axis analysis were applied to build the correlations for every trait pairs of each plant group, and then to compare the differences in the trait-trait correlations among different plant groups. Leaf Nmass and Pmass of two groups of aquatic plants (emergent and submerged plants) were higher, but N:P ratios were lower than those of two groups of terrestrial plants (sedges and grasses). Submerged plants had extremely high SLA, while grasses had the lowest SLA. Nmass positively correlated with Pmass in three out of four plant groups. The two terrestrial plant groups had positive Nmass-SLA relationships but these two traits coupled weakly in aquatic plants. Pmass showed positive relationships to SLA in three out of four plant groups. Significant shifts of trait-trait relationships between aquatic and terrestrial plants were observed. In general, aquatic plants, especially submerged plants, are characterized by higher SLA, greater leaf nutrientmass than terrestrial plants, tend to pursue fast-return investment strategies, and represent the acquisitive end of leaf economics spectrum. The deviations of trait-trait relationships between different plant groups reveal the precise adaptions of submerged plants to the unique aquatic habitats.

Protocol development for science based mapping of submerged aquatic vegetation (SAV) requires comprehensive ground truth data describing the full range of variability observed in the target. The Indian River Lagoon, Florida, extends along 250 km of the east central Florida coast adjacent to the Atlantic Ocean. The lagoon crosses the transition zone between the Caribbean and Carolinian zoogeographic provinces making it highly diverse. For large scale mapping and management of SAV four common and three uncommon species of seagrass (Tracheophyta) and three broad groups of macroalgae; red algae (Rhodophyta), green algae (Chlorophyta), and brown algae (Phaeophyta) are recognized. Based on technical and cost limitations we established twenty, 7-10 km long flight transects for collection of 1.2 m² spatial resolution hyperspectral imagery covering the length of the lagoon. Emphasis was placed on the area near the Sebastian River and adjacent Sebastian Inlet. Twenty six 40 m long ground truth transects were established in the lagoon using 1 m² white panels to mark each transect end. Each transect target was located in the field using high precision GPS. Transects were positioned to cover a range of depths, SAV densities, mixed and monotypic species beds, water quality conditions and general sediment types. A 3 m wide by 30 m long grid was centered on each transect to avoid spectral influences of the white targets. Water depth, species of seagrasses, estimates of vegetation cover percentage, estimates of epiphytic density, and measured canopy height were made for each 1 m² (n=90). This target based grid arrangement allows for identification and extraction of pixel based hyperspectral signatures corresponding to individual ground truth grid cells without significant concern for rectification and registration error.

Astronomic tides and nonlinear tidal dispersion for a tropical coastal estuary with engineered features (causeways): Indian River lagoon system

The Indian River Lagoon System (IRLS) has been impacted by the surrounding development, leading to excessive nutrient loads that have resulted in frequent and prolonged phytoplankton blooms in the northern reaches. Our study focused on estimating terrestrial groundwater discharge (TGD) and associated nutrient loads by combining field measurements and hydrogeologic modeling at four transects: Eau Gallie (EGT), River Walk (RWT), Banana River (BRT), and Mosquito Lagoon (MLT) across the IRLS. Multiple monitoring stations were installed to collect groundwater and surface water levels, salinity, and nutrient concentrations during 2014-2015. Samples were analyzed for dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP). Numerical modeling was accomplished using SEAWAT to simulate TGD rates, whereas nutrient loads were calculated by multiplying simulated TGD by measured concentrations. TGD rates and nutrient loads were also estimated specifically for the “near-shore zone” along each transect. The effect of recharge from underlying Hawthorn Formation was also evaluated by incorporating estimated recharge rates into the models. Porewater and lagoon water samples showed that ammonium predominated over (NO2+NO3) and PO4 at all sites, resulting in DIN/DIP ratio surpassing the Redfield ratio. Low nitrite/nitrate, coupled with elevated ammonium concentrations at RWT, BRT, and MLT, may be attributed to biogeochemical transformations catalyzed by mangroves and wetlands. Simulated TGD showed mild temporal but significant spatial variation, especially between EGT and RWT compared to BRT and MLT. The highest average TGD of 0.73 and 0.77 m3/d.m occurred at RWT and EGT, respectively, whereas the lowest rates were predicted at BRT and MLT. The highest estimated average DIN loads of 507 and 428 g/yr.m were received at EGT and RWT, respectively, whereas MLT and BRT exhibited lower loads. The DIP loads were remarkably lower than the DIN loads and were significantly different in space and time between sites. Elevated DIN combined with reduced DIP resulted in DIN/DIP exceeding the Redfield ratio, thereby encouraging the blooming of harmful algae. Although the majority of seepage occurs through the near-shore zone, small amounts are received along the entire transect at all sites. The Hawthorn Formation does not contribute significant recharge to the aquifer at the transect locations.

Seagrass protection and restoration in Florida’s Indian River Lagoon system (IRLS) is a mutual goal of state and federal programs. These programs require, the establishment of management targets indicative of seagrass recovery and health. We used three metrics related to seagrass distribution: areal coverage, depth limit, and light requirement. In order to account for the IRLS’s spatial heterogeneity and temporal variability, we developed coverage and depth limit targets for each of its 19 segments. Our method consisted of two steps: mapping the union of seagrass coverages from all availabe mapping years (1943, 1986, 1989, 1992, 1994, 1996, and 1999) to delineate wherever seagrass had been mapped and determining the distribution of depth limits based on 5,615 depth measurements collected on or very near the deep-edge boundary of the union coverage. The frequency distribution of depth limits derived from the union coverage, along with the median (50th percentile) and maximum (95th percentile) depth limits, serve as the seagrass depth targets for each segment. The median and maximum depth targets for the IRLS vary among segments from 0.8 to 1.8 and 1.2 to 2.8 m, respectively.Halodule wrightii is typically the dominant seagrass species at the deep-edge of IRLS grass beds. We set light requirement targets by using a 10-yr record of light data (1990–1999) and the union coverage depth limit distributions from the most temporally stable seagrass segments. The average annual light requirement, based on the medians of the depth limit distributions, is 33 ± 17% of the subsurface light. The minimum annual light requirement, based on of the 95th percentile of the depth distributions, is 20 ± 14%; the minimum growing season light requirement (March to mid September) is essentially the same (20 ± 13%). Variation in depth limits and light requirements, is probably due to factors other than light that influence the depth limit of seagrasses (e.g., competition, physical disturbance). The methods used in this study are robust when applied to large or long-term data sets and can be applied to other estuaries where grass beds are routinely monitored and mapped.

Fifteen species of elasmobranchs, eight sharks and seven rays, have been recorded with reasonable certainty from the Indian River lagoon system on the central east coast of Florida. We collected four shark and six ray species during a three and one-half year study of the northern portion of the lagoon system. Five of these appear to be year-round residents, and the remainder utilize the area only at restricted times of the year or as a nursery ground. The most abundant resident species areDasyatis sayi, D. sabina, andCarcharhinus leucas. Pristis pectinata, once a common resident species, has been extirpated from the lagoons. The distribution of ocean inlets and salinity appear to be major factors affecting diversity and numbers of elasmobranchs in the Indian River system.

Recently, there has been an expansion of submerged aquatic vegetation (SAV) in the tidal fresh and oligohaline portions of lower Chesapeake Bay tributaries. Much like the resurgence seen in the Potomac in the 1980’s, this spread of SAV in Virginia systems such as the Mattaponi, Pamunkey and Chickahominy seems to have been initiated by the introduction and spread of the invasive species Hydrilla verticillata, and appears to have been rapid. However the resurgence in the Piankatank has occurred in the absence of the introduction of this species. The factors that are influencing the growth of SAV in these tributary environments, including water quality and habitat conditions as well as the potential for interspecific competition between H. verticillata and the other SAV species in these regions are not well known. Annual aerial mapping surveys of the Chickahominy River were used alongside historical water quality data to investigate the patterns and rates of SAV bed development, and the relationships between this development and water quality conditions. Field investigations were performed in order to better understand the seasonal community dynamics relative to water quality conditions and interspecific competition. Historical analysis, field monitoring and field experimentation all showed salinity and turbidity to be the main factors controlling SAV abundance and species distribution along the Chickahominy River. Historical analysis of the Chickahominy River revealed a decline in SAV abundance in 2002, which corresponded with seasonal mean salinities of 4.1 psu. SAV abundance from 1998-2007 showed a significant correlation with vegetation emergence period secchi depth, in which secchi depths of 0.3 meters, the lowest of the time period, occurred during the 2002 SAV decline. Field data showed species zonation, in which H. verticillata was the overall dominant species, but was limited to the upper portion of the river where salinity intrusion remained below 2 psu throughout the growing season. Najas minor was dominant in the lower portion of the river where salinities reached over 4 psu in October. Salinity was the best predictor for H. verticillata’s biomass difference between the upper and lower river. SAV in the Chickahominy was able to grow in a wide range of conditions, with total suspended solids and chlorophyll a concentrations at times greater than 20 mg l and 40 μg l, respectively, and sediment organic content ranging from less than 1% to greater than 25%. Comparisons with the Mattaponi and Piankatank rivers revealed ideal habitat for H. verticillata growth in the Mattaponi, where salinities along the vegetated reach of the upper river did not extend above 1 psu. On the other hand, this species was not found growing in the Piankatank, where salinities in the very upper portion of the river reached 3.5 psu. Finally, a field species removal experiment demonstrated that environmental conditions rather than interspecific competition were most important in determining plant performance, as both H. verticillata and N. minor exhibited poor growth in the lower river site, which had higher salinity and turbidity levels than the upper river site. Influences of Habitat Conditions on Submerged Aquatic Vegetation Development in the Chickahominy River and other Virginia Tributaries of the Chesapeake Bay

Seagrass meadows are among the most threatened ecosystems on Earth, with losses attributed to increasing coastal populations, degraded water quality and climate change. As coastal communities work to improve water quality, there is increased concern regarding the use of herbicides within the watersheds of these sensitive ecosystems. Glyphosate is the most widely used herbicide on Earth because it is non-selective and lethal to most plants. Also, the targeted amino acid synthesis pathway of glyphosate is not carried out by vertebrates, and it is generally considered one of the safer but effective herbicides on the market. At least partially due to its cost-effectiveness compared to other techniques, including mechanical harvesting, glyphosate use in the aquatic environment has increased in coastal areas to manage aquatic weeds, maintain navigable waterways and mitigate upland flooding. This has prompted concerns regarding potential ecosystem-level impacts. To test the acute toxicity of glyphosate to seagrasses, mesocosm experiments exposed Ruppia maritima and Halodule wrightii to 1 ppm, 100 ppm and 1000 ppm of glyphosate (as glyphosate acid). No significant decrease in leaf chlorophyll a (Chl a) was identified for either species at 1 ppm versus a control; however, significant decreases were observed at higher concentrations. In all except 1000 ppm mesocosms, water column Chl a increased, with a 7-fold increase at 100 ppm. These data demonstrate that at very high glyphosate concentrations, both acute toxicity and light limitation from enhanced algal biomass may have adverse impacts on seagrasses. Despite these observations, no significant adverse impacts attributed to acute toxicity were observed at 1 ppm, which is >1000 times higher than concentrations measured in the Indian River Lagoon system. Overall, herbicide use and associated decaying biomass contribute nutrients to these systems, in contrast to the removal of nutrients when mechanical harvesting is used. Based on our data and calculations, when used at recommended application rates, contributions to eutrophication, degraded water quality and harmful algal blooms were more likely to impact seagrasses than acute toxicity of glyphosate.

Marine submerged aquatic vegetation (SAV) plays a vital role as habitats, nursery and feeding grounds for a wide range of marine aquatic and terrestrial life. Recently, remote sensing techniques have been successfully applied in marine benthic mapping in coastal waters. However, the majority of these techniques have focused on either seagrasses meadows or coral reefs. There are a few studies that have been published validating a methodology for mapping SAV on brown macroalgae (Sargassum spp., Ecklonia spp.), seagrasses, and/or other macroalgae groups by spectral response from remote sensing. Hence, we studied the in-situ optical properties of living macroalgae, seagrasses, and rubble. The spectral characteristics of varied SAV groups were measured using the high resolution FieldSpec® 4 Hi-Res portable spectroradiometer. The study site selected was the Shoalwater Islands Marine Park, Rockingham, Western Australia as it is one of the fifteen biodiversity hotspots in Australia. Correlation and Principle Component Analysis were employed to evaluate the differences between SAV groups. The results have documented the spectral features of SAV and their associated habitats in Shoalwater Islands Marine Park, Western Australia, and developed a spectral library to distinguish among seagrass species and algae groups (green, red, and brown benthic macroalgae). The implications of this study will contribute to estimate and detect the distribution and seasonal variation of SAV on a broader scale.

Effect of submerged aquatic vegetation on turbulence induced by an oscillating grid

Three species of sparids in the western Atlantic, sheepshead (Archosargus probatocephalus), sea bream (A. rhomboidalis), and pinfish (Lagodon rhomboides), share overlapping habitats, spawning seasons, and spawning grounds, providing opportunities for interaction among these species. Three regions of mitochondrial DNA and three nuclear DNA intron sequences were used to construct the genetic relationships among these species. The results showed that these species are closely related, suggesting the presence of soft polytomy with sheepshead and western Atlantic sea bream as sister species. However, western Atlantic sea bream and pinfish are equally divergent from sheepshead. We used a suite of 18 microsatellite markers to verify the occurrence of hybridization, identify the parental types, and evaluate the filial-generation status of 36 individuals morphologically identified as hybrids from the Indian River Lagoon system, in Florida. The 36 putative hybrids were analyzed with a reference group of 172 western Atlantic sea bream, 232 pinfish, and 157 sheepsheads and were all genetically determined to be F1 of sheepshead and western Atlantic sea bream with very little indication or no introgressive hybridization among the 172 reference specimens of western Atlantic sea bream. Hybridization was asymmetric, with western Atlantic sea bream males crossing with sheepshead females. Hybrids were first observed in the Indian River Lagoon in 2005, after the western Atlantic sea bream had become common there, in the 1990s. Their occurrence could be associated with unique features of the Indian River Lagoon that bring the two species together or with recent anthropogenic changes in this system. Further study is needed to determine the causes and long-term effects of the recurrent production of F1 hybrids and the degree of their sterility in the Indian River Lagoon.

A one-year survey of amphipods and tanaidaceans associated with monospecific sea grass meadows and a bare sand substratum, under similar physical-chemical conditions, showed that the magnozosterid Thalassia testudinum supported higher numbers of peracarids per square meter than the parvozosterid Halodule wrightii and the bare sand substratum as predicted by Kikuchi and Peres (1977). However, when examined in terms of numbers of individuals per unit sea grass biomass or surface area, Thalassia and Halodule supported nearly equal numbers ofepifauna. Syringodiumfiliforme, a syringodiid, consistently supported highest surface area-standardized abundances of epifauna. The previously reported significance of sea grass biomass in structuring crustacean assemblages held within, but not across, sea grass species. Although the amphipods and tanaids showed no species-specific association with sea grasses, the relative abundance of crustaceans was a function of both sea grass species and biomass. Relative abundance of infaunal types decreased from bare sand to Halodule to Syringodium to Thalassia sites and from low to high biomass sites. The abundance of peracarid crustaceans on sea grass meadows is a complex function of sea grass growth form and biomass which appear to mediate the distribution and foraging behavior of important predators. Despite evidence for strong parallelism among the animal communities of sea grass beds in different geographic regions (Ledoyer, 1964, 1969; Kikuchi, 1966, 1974; Nagle, 1968), Kikuchi and Peres (1977) pointed out that different sea grass species take distinct growth forms which affect the quality and nature of the habitat for small animals. Using the classification system of den Hartog (1967), the abundant sea grasses of the eastern United States are divided into magnozosterids (Zostera marina and Thalassia testudinum) with long, wide blades, parvozosterids (Halodule wrightil) with narrow blades, and syringodiids (Syringodium filiforme) with subulate blades. Because of high microhabitat diversity created by the wide blades, Kikuchi and Peres hypothesized that magnozosterids would support animal communities with higher biomass and species diversity than parvozosterids. Few studies have been designed to test for the role of sea grass species in the organization of associated fauna. Such a study requires closely spaced sites in monotypic beds of different sea grass species, all of which are characterized by similar physical-chemical conditions. In cases where conditions of station similarity have been met, significant differences were found in abundance, species composition, and species richness ofpolychaetes (Santos and Simon, 1974), crustaceans (Lewis, 1982), and fishes (Young, 1981; Stoner, in press) associated with different sea grass species. To test the hypothesis that various sea grass growth forms support different abundance and diversity of resident epifaunal organisms, peracaridan crustaceans were collected at seven closely spaced stations in Indian River lagoon, Florida. Three species of sea grass, Thalassia testudinum, Syringodiumfiliforme, and Halodule wrightii, represent the primary growth forms and are abundant in large beds in the lagoon. With care, it was possible to sample monospecific beds and bare sand substrata with similar depth and water conditions. Seasonal collections at the sites allowed an analysis of differences in species composition, faunal abun

Indications for Various Types of Operative Restorations for the Adult