Biology and ecology of athecate hydroids in Biscayne Bay, Florida: Potential use as bioindicators

This dissertation is a study evaluating the use of athecate hydroids as water quality bioindicators according to current EPA guidelines. The hydroid fauna of Biscayne Bay was examined to ascertain the relative abundance and distribution of taxon present. Both thecate and athecate hydroids were found within the bay; however, the distributions of the hydroids differed drastically. Athecate hydroids were found in great abundance in the eastern and western halves of the bay, while thecate hydroids were found predominantly in the eastern portions of the bay. The most abundant athecate hydroids were Eudendrium carneum and Halocordyle disticha. Reproduction and recruitment of both athecate hydroids was variable throughout the year.The distribution of E. carneum in Biscayne Bay suggested the ability of the hydroid to persist and adapt to the highly variable environmental conditions found in the western portions of the bay. Reciprocal transplants of E. carneum and H. disticha demonstrated competitive exclusion coaction and the ability to maintain exclusion in non-preferred habitats for both hydroids. Experimental laboratory testing using nutrients, Atrazine, Malathion, and Coppercide demonstrated E. carneum responded to alterations in ambient water quality on the time scale of 1 week by changes in overall colony size. Eudendrium carneum placed in various locations throughout Biscayne Bay responded with different changes in total colony size of to various water qualities found within the bay. Recommendations for further study and increased sensitivity analysis are included

The Forgotten Coast: A Synthesis of Current Knowledge of Southern Chukchi Sea Lagoon Ecosystems

In the Southern Chukchi Sea Region (SCSR) of the Alaskan Arctic, approximately 40% of the coastline consists of freshwater-brackish lagoons and the gravel spits that separate them from the ocean. These lagoons are important rearing, feeding, and spawning habitats for diverse fish and invertebrate assemblages composed of freshwater, diadromous, and marine taxa. Many of these species are prey for a suite of marine mammals and avian predators in addition to being important to the food security of subsistence users from the surrounding region. Despite recognition of the ecological and cultural importance of these habitats from as far back as the 1950s, the body of knowledge surrounding lagoons of the SCSR contains many knowledge gaps and fails to comprehensively capture the dynamic nature of both biotic and abiotic factors that define the functional ecology of these habitats. This report synthesizes the available knowledge of SCSR lagoons, including geomorphology, hydrology, food web structure, and local knowledge. We also recommend avenues of future study, such as characterizing the basal trophic levels of lagoon food webs. Only by constructing a more detailed and comprehensive knowledge base of SCSR lagoon ecology will management and conservation efforts in the region be able to address and mitigate potential threats resulting from expanding infrastructure and global climate change, while simultaneously supporting the diverse portfolio of lagoon habitats that have a vital role in regional subsistence practices and food security. Dans la région sud de la mer des Tchouktches (SCSR) de l’Arctique alaskien, environ 40 % du littoral est composé de lagunes d’eau douce et d’eau saumâtre ainsi que de flèches littorales en gravier les séparant de l’océan. Ces lagunes sont d’importants habitats d’alevinage, d’alimentation et de frai pour divers assemblages de poissons et d’invertébrés composés de taxons d’eau douce, de taxons diadromes et de taxons marins. Grand nombre de ces espèces servent de proies à un ensemble de mammifères marins et de prédateurs aviaires en plus de jouer un rôle important en matière de sécurité alimentaire chez les utilisateurs de subsistance de la région environnante. Même si la reconnaissance de l’importance écologique et culturelle de ces habitats remonte aux années 1950, l’ensemble de connaissances entourant les lagunes de la SCSR comporte de nombreux écarts et ne saisit pas entièrement la nature dynamique des facteurs biotiques et abiotiques qui définissent l’écologie fonctionnelle de ces habitats. Ce rapport synthétise les connaissances actuelles au sujet des lagunes de la SCSR, y compris la géomorphologie, l’hydrologie, la structure du réseau alimentaire et les connaissances locales. Nous recommandons aussi des possibilités d’études futures, comme la caractérisation des niveaux trophiques de base des réseaux alimentaires des lagunes. Seule l’élaboration d’une base de connaissances plus exhaustive et détaillée de l’écologie des lagunes de la SCSR permettra aux efforts de gestion et de conservation déployés dans la région de gérer et d’atténuer les menaces découlant de l’expansion des infrastructures et du changement climatique mondial tout en soutenant simultanément la gamme diverse d’habitats de lagunes qui jouent un rôle vital dans les pratiques de subsistance et la sécurité alimentaire de la région.

The influence of freshwater runoff on biomass, morphometrics, and production of Thalassia testudinum

Efforts to restore more natural freshwater flows in South Florida will impact Biscayne Bay. In order to evaluate possible effects of decreased freshwater discharge on the seagrass Thalassia testudinum, we determined the biomass, density, morphometrics (width, length, number of blades per shoot) and production of T. testudinum twice a year for 2 year at sites exposed to varying degrees of freshwater runoff. Responses to freshwater discharge varied between the sampling years. The only morphometric variable to be influenced by freshwater runoff in both years was blade width with width of seagrass blades being less at sites influenced by freshwater runoff than at sites with limited influence of freshwater runoff. In 1996, no other parameters differed among the three freshwater conditions considered; canal discharge, sheet-flow runoff, and limited freshwater runoff. In addition, all measured parameters were greater in summer (wet season) than in winter (dry season) in 1996. In 1997, biomass, shoot weight, shoot production, and areal shoot production all were greater at sites on the eastern side of the bay that experience limited influence from freshwater runoff compared to sites on the western side of the bay that experience large amounts of freshwater runoff from sheet-flow and canal discharge. In 1997, only length of seagrass showed a significant increase from winter to summer. Factors thought to be responsible for these interannual differences are winter temperatures and seasonal rainfall amounts. The winter of 1996 was much colder than the winter of 1997, and 1997 experienced an unusually rainy dry season thus increasing the amount of time during the year that freshwater runoff would be influencing sites on the western side of the bay. Based on these results, reduced freshwater inflow to Biscayne Bay should have a positive effect on T. testudinum provided detrimental hypersaline conditions do not occur