Benthic Exchange of C, N, and P Along the Estuarine Ecotone of Lower Taylor Slough, Florida (USA): Effect of Seasonal Flows and Phosphorus Availability

The southern Everglades and Florida Bay have experienced a nearly 50 % reduction in freshwater flow resulting in increased salinity and landward expansion of mangrove forest. Given the marine end-member is a natural source of P to this region, it is necessary to understand the interactions between inflows and P availability in controlling the exchange of materials across the mangrove ecotone. From 2007 to 2008, we used sediment core incubations to quantify fluxes of dissolved inorganic N and P and dissolved organic carbon (DOC) in three ecotone areas (dwarf mangrove, pond, and bay). Experiments were repeated seasonally over 2 years involving P-enriched surface water as a factor. We saw consistent uptake of soluble reactive P (SRP), DOC, and nitrate + nitrite (N+N) by the soils/sediments and release of ammonium (NH4 +) from soils/sediments to the water column across all sites and seasons. P enrichment had no discernible effect on DIN or DOC flux, suggesting that rapid P uptake may have been more geochemically mediated. However, uptake of added P occurred across all sites and seasons, reflecting high uptake capacity in this carbonate system and the potential of the mangrove ecotone to sequester P as it becomes more available.

Evidence of Recent Phosphorus Enrichment in Surface Soils of Taylor Slough and Northeast Everglades National Park

Everglades National Park (ENP) is the last hydrologic unit in the series of impounded marsh units that make up the present-day Everglades. The ENP receives water from upstream Water Conservation Areas via canals and water control structures that are highly regulated for flood control, water supply, wildlife management, concerns about poor water quality and the potential for downstream ecosystem degradation. Recent surveys of surface soils in ENP, designed for random sampling for spatial analysis of soil nutrients, did not sample proximate to inflow structures and thus did not detect increased soil phosphorus associated with these water conveyances. This study specifically addressed these areas in a focused sampling effort at three key inflow points in northeast ENP which revealed elevated soil TP proximate to inflows. Two transects extending down Shark River Slough and one down Taylor Slough (a natural watershed of particular ecological value) were found to have soil TP levels in excess of 500 mg kg−1—a threshold above which P enrichment is indicated. These findings suggest the negative impact of elevated water (P) from surface flows and support the assertion that significant soil TP enrichment is occurring in Taylor Slough and other areas of northeastern ENP.

A Suite of Prey Traits Determine Predator and Nutrient Enrichment Effects in a Tri-Trophic Food Chain

Predation, predation risk, and resource quality affect suites of prey traits that collectively impact individual fitness, population dynamics, and community structure. However, studies of multi-trophic level effects generally focus on a single prey trait, failing to capture trade-offs among suites of covarying traits that govern population responses and emergent community patterns. We used structural equation models (SEM) to summarize the non-lethal and lethal effects of crayfish, Procambarus fallax, and phosphorus (P) addition, which affected prey food quality (periphyton), on the interactive effects of behavioral, morphological, developmental, and reproductive traits of snails, Planorbella duryi. Univariate and multivariate analyses suggested trade-offs between production (growth, reproduction) and defense (foraging behavior, shell shape) traits of snails in response to non-lethal crayfish and P addition, but few lethal effects. SEM revealed that non-lethal crayfish effects indirectly limited per capita offspring standing stock by increasing refuge use, slowing individual growth, and inducing snails to produce thicker, compressed shells. The negative effects of non-lethal crayfish on snails were strongest with P addition; snails increased allocation to shell defense rather than growth or reproduction. However, compared to ambient conditions, P addition with non-lethal crayfish still yielded greater per capita offspring standing stock by speeding individual snail growth enabling them to produce more offspring that also grew faster. Increased refuge use in response to non-lethal crayfish led to a non-lethal trophic cascade that altered the spatial distribution of periphyton. Independent of crayfish effects, snails stimulated periphyton growth through nutrient regeneration. These findings illustrate the importance of studying suites of traits that reveal costs associated with inducing different traits and how expressing those traits impacts population and community level processes.

The Effect of Prenatal Auditory Enrichment on Perceptual Narrowing in Bobwhite Quail Neonates

The development of species-typical perceptual preferences has been shown to depend on a variety of socially and ecologically derived sensory stimulation during both the pre- and postnatal periods. The prominent mechanism behind the development of these seemingly innate tendencies in young organisms has been hypothesized to be a domain-general pan-sensory selectivity process referred to as perceptual narrowing, whereby regularly experienced sensory stimuli are honed in upon, while simultaneously losing the ability to effectively discriminate between atypical or unfamiliar sensory stimulation. Previous work with precocial birds has been successful in preventing the development of species-typical perceptual preferences by denying the organism typical levels of social and/or self-produced stimulation. The current series of experiments explored the mechanism of perceptual narrowing to assess the malleability of a species-typical auditory preference in avian embryos. By providing a variety of different unimodal and bimodal presentations of a mixed-species vocalizations at the onset of prenatal auditory function, the following project aimed to 1) keep the perceptual window from narrowing, thereby interfering with the development of a species-typical auditory preference, 2) investigate how long differential prenatal stimulation can keep the perceptual window open postnatally, 3) explore how prenatal auditory enrichment effected preferences for novelty, and 4) assess whether prenatal auditory perceptual narrowing is affected by modality specific or amodal stimulus properties during early development. Results indicated that prenatal auditory enrichment significantly interferes with the emergence of a species-typical auditory preference and increases openness to novelty, at least temporarily. After accruing postnatal experience in an environment rich with species-typical auditory and multisensory cues, the effect of prenatal auditory enrichment rapidly was found to rapidly fade. Prenatal auditory enrichment with extraneous non-synchronous light exposure was shown to both keep the perceptual narrowing window open and impede learning in the postnatal environment, following hatching. Results are discussed in light of the role experience plays in perceptual narrowing during the perinatal period.

TS/Ph-4 iron enrichment plots, Taylor Slough

This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DBI-0620409 and #DEB-9910514. This image is made available for non-commercial or educational use only.