Ecology of juvenile hawksbills (Eretmochelys imbricata) at Buck Island Reef National Monument, US Virgin Islands

Surveys of juvenile hawksbills around Buck Island Reef National Monument, US Virgin Islands from 1994 to 1999 revealed distributional patterns and resulted in a total of 75 individual hawksbill captures from all years; turtles ranged from 23.2 to 77.7 cm curved carapace length (CCL; mean 42.1 ± 12.3 cm SD). Juveniles concentrated where Zoanthid cover was highest. Length of time between recaptures, or presumed minimum site residency, ranged from 59 to 1,396 days (mean 620.8 ± 402.4 days SD). Growth rates for 23 juveniles ranged from 0.0 to 9.5 cm year^?1 (mean 4.1 ± 2.4 cm year^?1SD). Annual mean growth rates were non-monotonic, with the largest mean growth rate occurring in the 30–39 cm CCL size class. Gastric lavages indicated that Zoanthids were the primary food source for hawksbills. These results contribute to our understanding of juvenile hawksbill ecology and serve as a baseline for future studies or inventories of hawksbills in the Caribbean.     

Short- and long-term consistency in the foraging niche of wandering albatrosses

The wandering albatross (Diomedea exulans) is regarded as a generalist predator, but can it be consistent in its foraging niche at an individual level? This study tested short- and long-term consistency in the foraging niche in terms of habitat use, trophic level and, by inference, prey selection. Fieldwork was carried out at Bird Island, South Georgia, in May–October 2009, during the chick-rearing period. Blood (plasma and cells) and feathers for stable isotope analyses (δ¹³C and δ¹⁵N) were sampled from 35 adults on their return from a foraging trip during which they carried stomach temperature, activity and global positioning system loggers. Results suggest short-term consistency in foraging niche in relation to both oceanic water mass and trophic level, and long-term consistency in use of habitat. Consistent differences between individuals partly reflected sex-specific habitat preferences. The proportion of consistent individuals (i.e., with a narrow foraging niche) was estimated at c. 40?% for short-term habitat and trophic level (prey) preferences and 29?% for longer-term habitat preference, suggesting this is an important characteristic of this population and potentially of pelagic seabirds in general. Foraging consistency was not related to body condition or level of breeding experience; instead, it may reduce intraspecific competition.     

Mechanisms of moisture stress in a mid-latitude temperate forest: Implications for feedforward and feedback controls from an irrigation experiment

While it is well established that stomata close during moisture stress, strong correlations among environmental (e.g., vapor pressure deficit, soil moisture, air temperature, radiation) and internal (e.g., leaf water potential, sap flow, root-shoot signaling) variables obscure the identification of causal mechanisms from field experiments. Models of stomatal control fitted to field data therefore suffer from ambiguous parameter identification, with multiple acceptable (i.e., nearly optimal) model structures emphasizing different moisture status indicators and different processes. In an effort to minimize these correlations and improve parameter and process identification, we conducted an irrigation experiment on red maples (Acer rubrum L.) at Harvard Forest (summers of 2005 and 2006). Control and irrigated trees experienced similar radiative and boundary layer forcings, but different soil moisture status, and thus presumably different diurnal cycles of internal leaf water potential. Measured soil moisture and atmospheric forcing were used to drive a transient tree hydraulic model that incorporated a Jarvis-type leaf conductance in a Penman–Monteith framework with a Cowan-type (resistance and capacitance) tree hydraulic representation. The leaf conductance model included dependence on both leaf matric potential, Ψ_L (so-called feedback control) and on vapor pressure deficit, D (so-called feedforward control). Model parameters were estimated by minimizing the error between predicted and measured sap flow. The whole-tree irrigation treatment had the effect of elevating measured transpiration during summer dry-downs, demonstrating the limiting effect that subsurface resistance may have on transpiration during these times of moisture stress. From the best fitted model, we infer that during dry downs, moisture stress manifests itself in an increase of soil resistance with a resulting decrease in Ψ_L, leading to both feedforward and feedback controls in the control trees, but only feedforward control for the irrigated set. Increases in the sum-of-squares error when individual model components were disabled allow us to reject the following three null hypotheses: (1) the f(D) stress is statistically insignificant (p = 0.01); (2) the f(Ψ_L) stress is statistically insignificant (p = 0.07); and (3) plant storage capacitance is independent of moisture status (p = 0.07).     

Central place foraging by breeding Cook’s petrel Pterodroma cookii: foraging duration reflects range, diet and chick meal mass

Pelagic seabirds are central place foragers during breeding and variation in foraging trip duration and range reflect differences in diet and chick provisioning, through the exploitation of divergent habitats of varying productivity. We tested whether these relationships hold in small procellarriids by equipping chick-rearing Cook’s petrel Pterodroma cookii (200 g) with geolocation-immersion loggers, conducting isotope analysis of blood and measuring chick meal mass following foraging trips of varying duration. Cook’s petrel tracked during chick rearing from Little Barrier Island (LBI) and Codfish Island (CDF), New Zealand had larger maximum ranges during longer foraging trips. Blood nitrogen isotope signatures (δ¹⁵N) of adults were significantly higher after foraging trips of longer duration, but not of greater maximum range. There was no significant relationship between blood carbon isotope signatures (δ¹³C) and foraging trip characteristics. Proportion of time spent on the sea surface and the mass of the meal brought back to chicks were consistently greater for Cook’s petrel with larger maximum ranges, which in the case of birds from CDF coincided with productive subtropical convergence zone habitats. As predicted, trip duration reflected divergent foraging behaviours in Cook’s petrel during breeding. We suggest that the availability of different prey is a key factor governing at-sea distributions and dietary composition of this species.     

Use of toxicity identification evaluations to determine the pesticide mitigation effectiveness of on-farm vegetated treatment systems

Evidence of ecological impacts from pesticide runoff has prompted installation of vegetated treatment systems (VTS) along the central coast of California, USA. During five surveys of two on-farm VTS ponds, 88% of inlet and outlet water samples were toxic to Ceriodaphnia dubia. Toxicity identification evaluations (TIEs) indicated water toxicity was caused by diazinon at VTS-1, and chlorpyrifos at VTS-2. Diazinon levels in VTS-1 were variable, but high pulse inflow concentrations were reduced through dilution. At VTS-2, chlorpyrifos concentrations averaged 52% lower at the VTS outlet than at the inlet. Water concentrations of most other pesticides averaged 20-90% lower at VTS outlets. All VTS sediment samples were toxic to amphipods (Hyalella azteca). Sediment TIEs indicated toxicity was caused by cypermethrin and lambda-cyhalothrin at VTS-1, and chlorpyrifos and permethrin at VTS-2. As with water, sediment concentrations were lower at VTS outlets, indicating substantial reductions in farm runoff pesticide concentrations.     

Defecation by Salpa thompsoni and its contribution to vertical flux in the Southern Ocean

Measurements of the defecation rate of Salpa thompsoni were made at several stations during two cruises west of the Antarctic Peninsula in 2004 and 2006. Rates were quantified in terms of number of pellets, pigment, carbon and nitrogen for a wide size range of both aggregate and solitary salps. Measured defecation rates were constant over several hours when salps were held at near-surface conditions from which they had been collected. The defecation rate per salp increased with both salp size and the ambient level of particulate organic matter (POM) in the upper water column. The weight-specific defecation rate ranged between 0.5 and 6% day⁻¹ of salp body carbon, depending on the concentration of available particulate matter in the water. Carbon defecation rates were applied to biomass estimates of S. thompsoni to calculate daily carbon defecation rates for the populations sampled during the two cruises. Dense salp populations of over 400 mg C m⁻² were calculated to produce about 20 mg C m⁻² day⁻¹, comparable to other major sources of vertical flux of organic material in the Southern Ocean. Measured sinking rates for salp fecal pellets indicated that the majority of this organic material could reach deep sediments within a few days, providing a fast and direct pathway for carbon to the deep ocean.     

In-situ partitioning of butyltin compounds in estuarine sediments

The in-situ solid/pore-water partitioning of tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) was determined for an estuarine sediment profile collected from a commercial marina. Total butyltin levels exceeded sediment quality guideline values, and were 220-8750 microg/kg for TBT, 150-5450 microg/kg for DBT and 130-4250 microg/kg for MBT. Pore-water butyltin concentrations ranged from 0.05 to 2.35 microg/l for TBT, 0.07-3.25 microg/l for DBT, and 0.05-0.53 microg/l for MBT. The partitioning of butyltin compounds between the sediment solid-phase and pore-water was described by an organic carbon normalised distribution ratio (D(OC)). The observed D(OC) values were similar for TBT, DBT and MBT, and were 10(5)-10(6) l/kg. Values for the Butyltin Degradation Index (BDI) were larger than 1 at depths greater than 10 cm below the sediment/water-column interface. This indicates that substantial TBT degradation has occurred in the sediments, and suggests that natural attenuation may be a viable sediment remediation strategy.     

Decreased bioavailability of aminomethylphosphonic acid (AMPA) in genetically modified corn with activated carbon or calcium montmorillonite clay inclusion in soil

The widespread use of pesticides has resulted in detectable residues throughout the environment, sometimes at concentrations well above regulatory limits. Therefore, the development of safe, effective, field-practical, and economically feasible strategies to mitigate the effects of pesticides is warranted. Glyphosate is an organophosphorus herbicide that is degraded to aminomethylphosphonic acid (AMPA), a toxic and persistent metabolite that can accumulate in soil and sediment and translocate to plants. In this study, we investigated the binding efficacy of activated carbon (AC) and calcium montmorillonite (CM) clay to decrease AMPA bioavailability from soil and AMPA translocation to plants. Adsorption isotherms and thermodynamic studies on AC and CM were conducted and showed tight binding (enthalpy values >-20 kJ/mol) for AMPA with high capacities (0.25 mol/kg and 0.38 mol/kg, respectively), based on derivations from the Langmuir model. A hydra assay was utilized to indicate toxicity of AMPA and the inclusion of 1% AC and CM both resulted in 90% protection of the hydra (**p ≤ 0.01). Further studies in glyphosate-contaminated soil showed that AC and CM significantly reduced AMPA bioavailability by 53% and 44%, respectively. Results in genetically modified (GM) corn showed a conversion of glyphosate to AMPA in roots and sprouts over a 10-day exposure duration. Inclusion of AC and CM reduced AMPA residues in roots and sprouts by 47%–61%. These studies collectively indicate that AC and CM are effective sorbents for AMPA and could be used to reduce AMPA bioavailability from soil and AMPA residues in GM corn plants.     

Hot-blooded singers: endothermy facilitates crepuscular signaling in African platypleurine cicadas (Hemiptera: Cicadidae:<Emphasis Type="Italic"> Platypleura</Emphasis> spp.)

The cicada genus Platypleura has a wide distribution across Africa and southern Asia. We describe endothermic thermoregulation in four South African species that show crepuscular signaling behavior. This is the first evidence of thermoregulation in platypleurine cicadas. Field measurements of body temperature ( T _b) show that these animals regulate T _b through endogenous heat production. Maximum T _b measured was 22.1°C above ambient temperature during calling activity at dusk. The mean T _b during dusk activity did not differ from the mean T _b during diurnal activity. A unique behavior for cicadas, a temperature-dependent telescoping pulsation of the abdomen, was observed in the laboratory during endogenous warm-up. This behavior is part of a unique method of heat generation in endothermic cicadas. Males generally call from trunks and branches within the canopy and appear to use endothermy even when the sun is available to elevate T _b. Endothermy may provide the cicadas with the advantage of decreasing predation and acoustic competition by permitting calling from perches that most complement their cryptic coloration patterns and that ectotherms cannot use due to thermal constraints. In addition, endothermy may permit calling activity during crepuscular hours when atmospheric conditions are optimal for acoustic communication and predation risks are minimal.