Sanibel Island Research Articles

Microbial assessment of the ecological linkage between a red tide of Karenia brevis and bottom water anoxia off the coast of Fort Myers and Sanibel Island, Florida

Coastal ecosystem management necessitates a comprehensive understanding of the physical, chemical, and biological components and their interplay with socio-economic activities. Red tides of Karenia brevis reoccur almost annually on the West Florida Shelf and cause significant human and environmental health problems that often result in negative economic impacts. It is crucial that we understand the processes and dynamics of both phytoplankton and microbial communities as conditions necessary for the formation of hypoxia and anoxia in the coastal ecosystem. With the aim of identifying key microbial communities responsible for anoxia, we investigated the 2017–2018 Karenia bloom. Various water quality parameters, phytoplankton, and microbial community compositions were studied at eight sites on the West Florida Shelf. K. brevis densities were highest at the site of the plume of the Caloosahatchee River. At the site with the highest K. brevis abundance (6.3 ×106 cells/L), dissolved oxygen (DO) was supersaturated (303 %) at the surface, and the chlorophyll a concentration was 118 µg/L. The highest bacterial cell count (9.0 ×106 cells/mL) and the lowest bacterial diversity were also observed at this site. The bacterial community determined by high-throughput amplicon sequencing at this bloom site was unique and dominated by Bacteroidetes, which occupied 65 % of the relative abundance of the microbial community. The bottom water was generally hypoxic (mean ± SD: 0.98 ± 1.13 mg/L), with select stations having DO as low as 0.06 mg/L (anoxic). The anoxic bottom water harbored unique microbial taxa that were associated with the low oxygen conditions. Significant negative correlations were found between DO and the relative abundance of Deltaproteobacteria, Firmicutes, Spirochaetes, and unclassified Proteobacteria. Our investigation lays the groundwork for subsequent studies delving into the responses of phytoplankton and microbial communities to disturbances caused by Karenia blooms, as well as future strategies for mitigation and ecosystem restoration.

Field observations of Hurricane Ian’s wave and surge impact in the areas of Fort Myers Beach and Sanibel Island, USA

On September 18, Category 4 Hurricane Ian made landfall near Fort Myers Beach and Sanibel Island, two barrier islands on the northern Gulf of Mexico. In this paper, we present a novel set of observations from a post-event High Water Mark field survey as well as wavelet analysis of in-situ wave data. We also present a qualitative overview of some erosive effects and infrastructure damage. Measured peak surge elevations exceed 5 m, and wave plus surge elevations exceed 6.0 m (NAVD88). High Water Mark observations are consistent within the expected range produced by numerical hindcast models. A wavelet analysis, from one of the few wave records available during the storm, demonstrates the presence of long-period basin mode waves at a 40-min period. The 40-min wave appeared on the wave record before the storm surge, and the peak of this motion also occurred before the peak of the surge. In addition, the wavelet analysis reveals the presence of infragravity wave energy (periods between 30 s and 20 min). Together, these intermediate and long-period waves add over 40 cm to the total water level at peak energy. The measured field data shows a rapidly decreasing surge elevation within the first 300 m from the pre-storm shoreline, and we observe no statistically meaningful attenuation difference between the highly developed shoreline of Fort Myers and the more vegetated shoreline of Sanibel Island. However, the structural survey team observed more infrastructure damage in Fort Myers than Sanibel Island.

Climate change likely to increase co-occurrence of island endemic and invasive wildlife

Climate change is altering the distribution of wildlife across the globe. These distributional changes, paired with the environmental and vegetative shifts that spurred them, are likely to change co-occurrence patterns and interspecific interactions of native and invasive wildlife. A mesocosm of global change, we worked on Sanibel Island; a low-lying ∼4,900 ha barrier island in southwestern Florida, USA. Sanibel Island possessed a freshwater interior lined with mangrove forests to the north. Sanibel was ∼50% developed, ∼50% conserved, hydrologically degraded, shrub-encroached, and susceptible to inundation by sea-level rise. We used a Bayesian multispecies occupancy modeling approach to investigate how the effects of climate change might change co-occurrence patterns of 2 native island-endemic species (Sanibel Island rice rat [Oryzomys palustris sanibeli]; insular hispid cotton rat [Sigmodon hispidus insulicola]) and 1 exotic invasive species (black rat [Rattus rattus]). We found that co-occurrence is likely to increase between cotton rats and black rats with unknown impacts on interspecific interactions. We also found that climate change may threaten the persistence of cotton rats and black rats on Sanibel Island, but not rice rats so long as mangrove forests persist. Broadly our research demonstrates the importance of investigating interactions between climate change and co-occurrence when assessing contemporary and future wildlife distributions.

Shrub encroachment threatens persistence of an endemic insular wetland rodent

AbstractShrub encroachment is altering the structure and species composition of natural communities across the globe. However, little research has focused on how shrub encroachment influences wetland vertebrates, including small mammals. We sought to determine how vegetative structure and shrub cover influenced the occurrence of a threatened semiaquatic mammalian subspecies, the Sanibel Island rice rat (Oryzomys palustris sanibeli). We evaluated the influence of vegetation and metrics of inundation on probability of occurrence and localized seasonal colonization and extinction rates of the Sanibel Island rice rat over a 3-year period. We found Sanibel Island rice rats on 18 (33.3%) of our 54 sites. Their occurrence was positively associated with greater sand cordgrass (Spartina bakeri) cover and increased elevation, but negatively associated with greater shrub cover. Their probability of localized colonization was negatively associated with greater shrub cover. Localized extinction probabilities for Sanibel Island rice rats were positively associated with increased rainfall totals in the preceding 3 months and greater shrub cover. Using aerial photography from across the Sanibel Island rice rat’s range, we found 5.5-fold greater shrub cover in 2015 than in 1944. We suggest that increases in shrub cover and reduced cordgrass cover may be driving the decline of this once ubiquitous endemic species and that the encroachment of freshwater wetlands requires greater attention due to its potential to imperil wetland-dependent wildlife.

Termination of the 2018 Florida red tide event: A tracer model perspective

The 2018 Karenia brevis harmful algal bloom experienced along the west coast of Florida was the worst red tide occurrence there since 2005. Cell concentrations peaked in early fall of 2018, lessened in winter, and disappeared early in 2019. Here we examine the termination of this red tide event by using hindcast simulations of the West Florida Coastal Ocean Model, a numerical ocean circulation model that downscales from the deep Gulf of Mexico, across the continental shelf and into the estuaries. The underlying hypothesis is that without an offshore source of K. brevis cells, a nearshore bloom may quickly dissipate under the influence of a persistent upwelling circulation. To test this hypothesis, we used a passive tracer (without consideration of biological growth or decay) in the model to virtually indicate K. brevis cells. The tracer, inputted along the central West Florida coast where highest bloom concentrations were observed, was subsequently transported southward along the coast and offshore, significantly reducing the tracer concentrations over the three-month-long experimental duration, as was observed for the actual K. brevis cell concentrations. Whereas modeled tracer concentrations decreased over most of the West Florida coast, relatively higher concentrations remained just south of Sanibel Island, trapped there by the sharp bend in the coastline. Longer residence time for this area has important K. brevis implications. Lake Okeechobee nutrient flux through the Caloosahatchee River was thought to contribute to red tide in this region, and while these inputs may be a factor, a persistent upwelling circulation may also play a contributing role.

The influence of Lake Okeechobee discharges on Karenia brevis blooms and the effects on wildlife along the central west coast of Florida

Blooms of the dinoflagellate Karenia brevis (K. brevis) are a common occurrence in the Gulf of Mexico, especially along Florida's coast. The blooms produce brevetoxins, potent neurotoxins that are associated with mortalities of marine wildlife. In recent years, K. brevis blooms seem to have become more frequent and intense. The cause of these suspected increases is highly debated, with one suggested explanation being anthropogenic eutrophication. Patient records from the Clinic for the Rehabilitation of Wildlife (CROW) on Sanibel Island, Florida, USA, and K. brevis cell count samples from the west coast of Florida were used to assess trends in red tides and affected wildlife. Flow data from the Okeechobee waterway was used to investigate if discharges from Lake Okeechobee and the Caloosahatchee Estuary, where eutrophication is present, influence red tides along Florida's central west coast. Overall, K. brevis blooms show trends of increasing intensity and duration along Florida's coast between 1954 and 2020 (latest data available). This means the amount of wildlife affected will likely increase in the future, as a linear relationship was found between the number of admissions to CROW and K. brevis densities. Furthermore, water discharges from the Okeechobee waterway (including Lake Okeechobee and the Caloosahatchee Estuary) into the Gulf of Mexico were significantly correlated with K. brevis densities, which suggests that anthropogenic pollution might play a role in the observed increases. Clear correlations were found between K. brevis densities and brevetoxicosis patient numbers admitted, and this was strongest with overall admissions lagging 23 days behind cell counts. This further confirms brevetoxins as the likely cause of their morbidity and supports previous research on brevetoxin retention in the environment. Different species groups had significant correlations with K. brevis cell counts, double-crested cormorants showing the strongest link, and there were significant differences between these groups in lag times. The differences are likely due to their distinct foraging behaviours or susceptibilities to brevetoxins. These findings can help predict future trends in red tides and can guide further research on the effects of discharges on K. brevis blooms.

Multi-proxy characterization of storm deposits on Sanibel Island, Florida: A modern analog for paleotempestology

Hurricanes have serious impacts on human lives and infrastructure, especially as a result of flooding caused by storm surge and precipitation. To better prepare coastal populations for future hurricanes due to an increasingly warming world, a better understanding of hurricane storm surge is key. Southwest Florida is particularly vulnerable to hurricane storm surge where most of the coastline is within 2.5 m of sea level and population is on the rise (2.5% between 2019 and 2020 in Lee County). This study presents a geologic record of intense hurricane strikes from Sanibel Island dating back to approximately ca. 1920. Based on sedimentary proxies such as grain size, organics, moisture content, and calcium carbonate, three tempestites were identified in cores from the Sanibel Island Marsh. Radiometric dating constrained Tempestite 1 as Hurricane Donna (1960) and Tempestites 2 and 3 as the 1926 Great Miami Hurricane and the Tampa Bay hurricane of 1921. Of the eight intense hurricanes (category 3–5) taking place between ~1920–2016, only three hurricanes were recorded in the geologic record. Tempestites 1, 2, and 3 were deposited by intense, large radius storms with significant storm surge, which would indicate that at least three storms made significant impact on the Southwest Florida region between ~1920–1960. Since 1960 no storms have breached the Sanibel Island barrier. It is important for the public to recognize that even though this region has not experienced significant storm surge in the last ~60 years, several hurricanes occurring between 1920 and 1960 produced storms surges greater than ~10 ft. that were able to breach a major barrier island (Sanibel Island). Human-induced climate change is predicted to increase storminess and sea level rise in Southwest Florida with concomitant risk for future storm surge.

Vascular flora of J. N. “Ding” Darling National Wildlife Refuge, Sanibel Island, Florida, U.S.A.

The objective of this study was to collect and document the vascular plant species at the 2104-hectare J. N. “Ding” Darling National Wildlife Refuge, Sanibel Island, Florida. Vascular plant species were collected at two-month intervals from May 2014 to October 2017 during which we identified 319 species in 251 genera in 93 families. The Poaceae (41 spp.), Fabaceae (30 spp.), and Asteraceae (33 spp.) were the largest families. The most species rich genera were Euphorbia (8 spp.), Cyperus, Tillandsia (7 spp.), and Ipomoea (6 spp.). Eighty species; 25 percent of the flora, were non-native. One rare species occurred at the study site.

A floristic inventory and reassessment of the Flora of Sanibel Island (Lee Co.), Florida, U.S.A.

Sanibel Island (Lee Co., Florida) manifests eight main categories and 12 subcategories of habitats, and individual plant taxa occupy habitat(s) from one or more of those categories. Documented, presently as growing wild/apparently wild on Sanibel Island are individuals of 119 families, 397 genera, 611 species (including two hybrids), and 621 infrageneric taxa of vascular plants. Of the 621 infrageneric taxa, 420 (67.6%) are native and 13 (2.1 %) are endemic to Florida. We interpret the Island’s flora in terms of its history of severe natural and artificial disturbances.

Mycoplasma agassizii, an opportunistic pathogen of tortoises, shows very little genetic variation across the Mojave and Sonoran Deserts.

Mycoplasma agassizii is a common cause of upper respiratory tract disease in Mojave desert tortoises (Gopherus agassizii). So far, only two strains of this bacterium have been sequenced, and very little is known about its patterns of genetic diversity. Understanding genetic variability of this pathogen is essential to implement conservation programs for their threatened, long-lived hosts. We used next generation sequencing to explore the genomic diversity of 86 cultured samples of M. agassizii collected from mostly healthy Mojave and Sonoran desert tortoises in 2011 and 2012. All samples with enough sequencing coverage exhibited a higher similarity to M. agassizii strain PS6T (collected in Las Vegas Valley, Nevada) than to strain 723 (collected in Sanibel Island, Florida). All eight genomes with a sequencing coverage over 2x were subjected to multiple analyses to detect single-nucleotide polymorphisms (SNPs). Strikingly, even though we detected 1373 SNPs between strains PS6T and 723, we did not detect any SNP between PS6T and our eight samples. Our whole genome analyses reveal that M. agassizii strain PS6T may be present across a wide geographic extent in healthy Mojave and Sonoran desert tortoises.

The Modern Paleotempestology Record for Sanibel Island, Florida

The Modern Paleotempestology Record for Sanibel Island, Florida

<p><strong><em>Eucheumatopsis sanibelensis</em> <em>sp. nov.</em> from the Gulf coast of Florida, USA</strong></p>

Based upon COI-5P, LSU rDNA and rbcL sequence data, as well as its morphological characteristics, a new red algal species, Eucheumatopsis sanibelensis E.S.Peterson, C.W.Schneider et G.W.Saunders sp. nov., was discovered on the Gulf coast of Florida, USA and shown to be distinct from the generitype E. isiformis with a type locality in the eastern Caribbean Sea. The new more attenuate taxon from Sanibel Island represents only the second species in this newly described genus, a genus recently segregated from Eucheuma based upon significant molecular and morphological differences. The two species have overlapping geographic distributions in the eastern Gulf of Mexico, but thus far E. sanibelensis is only known from a single location.

Long-term pumping-induced groundwater quality changes at a brackish-water desalination facility, Sanibel Island, Florida

Long-term pumping-induced groundwater quality changes at a brackish-water desalination facility, Sanibel Island, Florida

Female loggerhead sea turtles (Caretta caretta L.) rarely remate during nesting season.

The goal of this study was to assess the consequences of single versus multiple paternity by identifying paternity of clutches per female to identify whether there were detectable costs or benefits. Multiple mating can occur when the benefits of mating outweigh the costs, but if costs and benefits are equal, no pattern is expected. Previous research on loggerhead sea turtle (Caretta caretta) populations found male‐biased breeding sex ratios and multiple mating by many females nesting in southwestern Florida. A sample of nesting loggerhead females who laid more than one nest over the course of the season and a subset of their hatchlings were examined from 36 clutches in 2016 on Sanibel Island, Florida. Males that fathered hatchlings in the first clutch sampled were identified in subsequent clutches. Interestingly, 75% of the females analyzed had mated singly. No male was represented in more than one female's clutches. The results suggest that females likely mate at the beginning of the season and use stored sperm for multiple clutches. Evidence for mating between laying events was limited. There was no consistent pattern across the subsequent multiple paternity clutches, suggesting benefits to loggerhead females likely equal their costs and subsequent mating is likely determined by female preference.

Determining the Sources of Macroalgae During Beach Stranding Events from Species Composition, Stable Isotope Analysis, and Laboratory Experiments

Large accumulations of stranded macroalgae on the beaches of Sanibel Island from 2004 to 2007 were unusual and thought to be driven by high rainfall and river flows stemming from a high frequency of hurricanes. The southwest Florida shelf was thought to be isolated from far-field effects such as high river flows and urbanization but field- and laboratory-based studies suggest that nitrogen enrichment, fragmentation, and species composition of macroalgal communities on the shelf and in the estuary contribute to beach stranding events. Macroalgae were sampled using a belt transect method to determine species distribution and abundance. Macroalgae were abundant (1) in the lower estuary with abundant seagrass and (2) on limestone outcroppings in the Gulf of Mexico. An MDS analysis of the quadrat samples indicated two distinct macroalgal community types, a “Sound” assemblage around Pine Island Sound and a “Gulf” assemblage, associated with a live bottom and patch reef in the Gulf of Mexico. Peak abundances for the two community types differed with the Gulf having peak abundances from July to November, while peak abundances in the Sound occurred from January to July. Sound macroalgal tissue had significantly enriched δ15N compared to Gulf tissue when all species were combined and in five of six species collected at both locations suggesting that stable isotope analysis could be useful in combination with species composition in determining the source of macroalgae during stranding events. In addition, a laboratory study was conducted on four species that were sampled and frequently collected as a result of stranding events. Laboratory growth experiments demonstrated the potential for three of four common species (Solieria filiformis, Gracilaria tikvahiae, Agardhiella subulata) to fragment and grow significantly more under elevated nitrate conditions.

A Veliconcha Unveiled: Observations on the Larva and Radula ofConus spurius, with Implications for the Origin of Molluscivory inConus

The veliconcha larva of the predatory gastropod Conus spurius Gmelin, 1791 is described and for the first time illustrated based on material from Sanibel Island, Florida. Hatchling veliconchas were 1470–1570 μm (mean = 1530) long, with first protoconch whorl maximum diameter 670–740 μm (mean = 710), and estimated egg diameter 570 μm. Veliconchas can swim for a few minutes to a few hours before settling. They have well-developed paired velar lobes each 600–700 μm in length, an extensible foot with a distinct metapodium separated from the remainder of the foot by a transverse fold, and operculum. Several early life history traits of C. spurius, particularly hatching as large veliconcha larvae with predominantly lecithotrophic, nearly non-planktonic development, closely resemble those of a well-defined clade of Conus Linnaeus, 1758 species that prey on other gastropods. They contrast with the majority of species in this hyperdiverse genus, which hatch as much smaller planktonic, obligatory planktotrophic veliger larvae. As adults they comprise a vermivorous feeding guild, preying exclusively or nearly so on polychaete annelids. Limited data suggest that C. spurius may share this trait with them but it may also prey on molluscs. Recent molecular phylogenetic trees suggest that the characters “pelagic development” and “non-pelagic development” (or nearly so: <1 day) are distributed independently of phylogeny in the larger clade that includes C. spurius and the molluscivorous species. Similarities in veliconcha morphology and developmental mode, adult radular tooth morphometry, phylogenetic position, and earliest fossil records suggest the speculative hypothesis that the monophyletic clade of extant molluscivorous Conus species may have evolved in the Miocene from a vermivore or mixed vermivorous-molluscivorous ancestor with these attributes, such as C. spurius.

Per-Olov Löwdin – father of quantum chemistry

ABSTRACTDuring 2016, we celebrate the 100th anniversary of the birth of Per-Olov Löwdin. He was appointed to the first Lehrstuhl in quantum chemistry at Uppsala University in 1960. Löwdin introduced quantum chemistry as a field in its own right by formulating its goals, establishing fundamental concepts, like the correlation energy, the method of configuration interaction, reduced density matrices, natural spin orbitals, charge and bond order matrices, symmetric orthogonalisation, and generalised self-consistent fields. His exposition of partitioning technique and perturbation theory, wave and reaction operators and associated non-linear summation techniques, introduced mathematical rigour and deductive order in the interpretative organisation of the new field. He brought the first computer to Uppsala University and pioneered the initiation of ‘electronic brains’ and anticipated their significance for quantum chemistry. Perhaps his single most influential contribution to the field was his education of two generations of future faculty in quantum chemistry through Summer Schools in the Scandinavian Mountains, Winter Institutes at Sanibel Island in the Gulf of Mexico. Per-Olov Löwdin founded the book series Advances in Quantum Chemistry and the International Journal of Quantum Chemistry. The evolution of quantum chemistry is appraised, starting from a collection of cross-disciplinary applications of quantum mechanics to the technologically advanced and predominant field of today, virtually used in all branches of chemistry. The scientific work of Per-Olov Löwdin has been crucial for the development of this new important province of science.

Three dimensional model evaluation of physical alterations of the Caloosahatchee River and Estuary: Impact on salt transport

Numerical hydrodynamic modeling provides quantitative understanding of how physical alterations of an estuary may alter the waterbody hydrodynamics and the rate of mixing with the ocean. In this study, a three dimensional hydrodynamic model (CH3D) was used to compare simulated salinities between the existing condition and five historical cases representing varying physical alterations of the Caloosahatchee Estuary involving (1) removal of the headwater structure (S-79); (2) removal of the downstream causeway to Sanibel Island; (3) backfilling an oyster bar near the estuary month; (4) refilling the navigation channel; and (5) the pre-development bathymetric condition. The results suggested that some alterations including the Sanibel Causeway, backfilling the oyster bar and the S-79 structure may have some local effects but did not change estuarine salinity structure significantly. Refilling the navigation channel had a more profound effect, resulting in a dry season salinity reduction of about 5 when compared with the existing condition. The reduced salt transport was more pronounced with the pre-development bathymetry because the estuary as a whole was much shallower than today. The significant system-wide increase in salt transport caused by the historic dredging of the navigation channel in the Caloosahatchee Estuary has significant implications in the development of attainable environmental flow targets for protecting the estuarine ecosystem.

Stony coral (Milleporidae and Scleractinia) communities in the eastern Gulf of Mexico: a synopsis with insights from the Hourglass collections

The eastern Gulf of Mexico is a complex mosaic of coral reefs and epibenthic communities. Although it is a large area of approximately 225,000 km2, only a small portion sustains viable coral reefs. In the lower margins of the eastern Gulf of Mexico (Key West to Dry Tortugas, 24°33'N), the coral reef communities are speciose and very similar to Caribbean coral reefs. Controlling factors influencing the distribution of the hydrozoan Millepora and Scleractinian species include climate, the lack of a consistent current system to support larval transport, and stochastic disturbances, such as red tide-harmful algal blooms, hurricanes, and winter frontal passages. In the eastern Gulf of Mexico region north of 26°N (Naples), the fauna is more eurytopic; characteristic species inhabiting the rocky hard bottom include Cladocora arbuscula (Lesueur, 1820), Siderastrea radians (Pallas, 1766), Solenastrea hyades (Dana, 1846), Manicina areolata (Linnaeus, 1758), and Isophyllia sinuosa (Ellis and Solander, 1786). Isolated locations, such as the Florida Middle Grounds and Pulley Ridge, sustain the more reef-dwelling-stenotopic species: Leptoseris cuccullata (Ellis and Solander, 1786); Dichocoenia stokesi Milne-Edwards and Haime, 1848; and Meandrina meandrites (Linnaeus, 1758). The present study focuses on the Hourglass collection of Scleractinian coral samples collected from August 1965 through November 1967 in the eastern Gulf of Mexico offshore of Tampa Bay (27°35'N) and Sanibel Island (26°24'N), from 6 to 73 m depths.

Genetic divergence of insular marsh rice rats in subtropical Florida

Three island populations of the marsh rice rat (Oryzomys palustris) found in Florida have been described as taxonomically unique; the Pine Island rice rat (O. p. planirostris) and Sanibel Island rice rat (O. p. sanibeli), originally described as subspecies, and the endangered silver rice rat (O. argentatus), originally described as a separate species. We aimed to resolve the phylogenetic relationships among these island populations and investigate their genetic distinctness with DNA sequence data from the mitochondrial control region and cytochrome-b gene. Using parsimony, maximum-likelihood, and Bayesian analyses, we estimated the phylogenetic relationships and genetic distances among the 3 island populations and 4 other described subspecies. Our mitochondrial DNA analyses indicate that the silver rice rat and Sanibel Island rice rat are genetically divergent from mainland populations, but the Pine Island rice rat is not. The silver rice rat and Sanibel Island rice rat may be genetically isolated due to geographic separation resulting in reduced gene flow. They have the potential to become distinct phylogenetic groups and eventually species.