Benthic diversity gradients and shifting baselines: implications for assessing environmental status

The increasing pressure on marine biodiversity emphasizes the importance of finding benchmarks against which to assess change. This is, however, a notoriously difficult task in estuarine ecosystems, where environmental gradients are steep, and where benthic biodiversity is highly variable in space and time. Although recent emphasis on diverse, healthy benthic communities in legislative frameworks has increased the number of indices developed for assessing benthic status, there is a lack of quantitative baselines in benthic diversity that would enable comparisons across broad spatial scales, encompassing different environmental settings and bioregions. By taking advantage of long-term monitoring data, spanning hundreds of stations over the past 40 years, we provide a comprehensive analysis of benthic a, beta, and gamma diversity, encompassing the entire' salinity gradient of the open sea areas of the large, brackish-water Baltic Sea. Using a relatively simple measure, average regional diversity, we define area-specific reference conditions and acceptable deviation against which to gauge current conditions in benthic macrofaunal diversity. Results show a severely impaired condition throughout large areas of the Baltic for the assessment period 2001-2006. All ecosystems are plagued by baselines that shift in time and space, and their definition is not trivial, but average regional diversity may offer a transparent way to deal with such changes in low-diversity systems. Identifying baselines will be of increasing importance given the potential of climatic drivers to interact with local anthropogenic stressors to affect patterns of biodiversity. Our analysis provides an evaluation of the current condition in a system that has been heavily influenced by anthropogenic impact and changing oceanographic conditions, and it provides a basis for future impact assessment and ecosystem-based management.     

New approach to calculate the probability of ignition

The probabilistic approach to the evaluation of fire hazard and the effectiveness of fire-precaution measures enables a rational response to the randomness of fire outbreaks. This article employs the statistical analysis methods to elucidate the causes for the ignition of fire on a random sample of industrial buildings in the Republic of Slovenia. The analyses are based on the Structural Equation Modeling (SEM), which is a well established and important statistical analysis technique in the fields of social science, biology, psychology and medicine, but hitherto rarely applied in safety research. The results of the study demonstrate that for the analyzed random sample of industrial buildings the frequency of fire outbreaks statistically significantly depends only on the presence and the probability of exposure to the heat sources (flames, sparks, and hot surfaces), but does not significantly depend on the available quantity of flammable materials within the industrial structure.     

Heart rate variability and motion sickness during forklift simulator driving

The goal of the study was to determine the effect of a 1-h hour long forklift truck virtual simulator driving on the mechanism of autonomic heart rate (HR) regulation in operators. The participants were divided into 2 subgroups: subjects with no definite inclination to motion sickness (group A) and subjects with a definite inclination to motion sickness (group B). Holter monitoring of electrocardiogram (ECG) signal was carried out in all subjects during the virtual simulator driving. For 12 consecutive epochs of ECG signal, HR variability analysis was conducted in time and frequency domains. In subjects with a definite inclination to motion sickness after ~30 min of the driving, changes in parameter values were found indicating an increase in sympathetic and parasympathetic activity with parasympathetic dominance.     

Evaluation of sound exposure and risk of hearing impairment in orchestral musicians

This study aimed to assess exposure to sound and the risk of noise-induced hearing loss (NIHL) in orchestral musicians. Sound pressure level was measured in 1 opera and 3 symphony orchestras; questionnaires were filled in. On the basis of that data, the risk of NIHL was assessed according to Standard No. ISO 1999:1990. Classical orchestral musicians are usually exposed to sound at equivalent continuous A-weighted sound pressure levels of 81?90 dB (10th?90th percentiles), for 20?45 h (10th?90th percentiles) per week. Occupational exposure to such sound levels over 40 years of employment might cause hearing loss (expressed as a mean hearing threshold level at 2, 3, 4 kHz exceeding 35 dB) of up to 26%. Playing the horn, trumpet, tuba and percussion carries the highest risk (over 20%).     

A stochastic model for estimating sustainable limits to wildlife mortality in a changing world

Human-caused mortality of wildlife is a pervasive threat to biodiversity. Assessing the population-level impact of fisheries bycatch and other human-caused mortality of wildlife has typically relied upon deterministic methods. However, population declines are often accelerated by stochastic factors that are not accounted for in such conventional methods. Building on the widely applied potential biological removal (PBR) equation, we devised a new population modeling approach for estimating sustainable limits to human-caused mortality and applied it in a case study of bottlenose dolphins affected by capture in an Australian demersal otter trawl fishery. Our approach, termed sustainable anthropogenic mortality in stochastic environments (SAMSE), incorporates environmental and demographic stochasticity, including the dependency of offspring on their mothers. The SAMSE limit is the maximum number of individuals that can be removed without causing negative stochastic population growth. We calculated a PBR of 16.2 dolphins per year based on the best abundance estimate available. In contrast, the SAMSE model indicated that only 2.3–8.0 dolphins could be removed annually without causing a population decline in a stochastic environment. These results suggest that reported bycatch rates are unsustainable in the long term, unless reproductive rates are consistently higher than average. The difference between the deterministic PBR calculation and the SAMSE limits showed that deterministic approaches may underestimate the true impact of human-caused mortality of wildlife. This highlights the importance of integrating stochasticity when evaluating the impact of bycatch or other human-caused mortality on wildlife, such as hunting, lethal control measures, and wind turbine collisions. Although population viability analysis (PVA) has been used to evaluate the impact of human-caused mortality, SAMSE represents a novel PVA framework that incorporates stochasticity for estimating acceptable levels of human-caused mortality. It offers a broadly applicable, stochastic addition to the demographic toolbox to evaluate the impact of human-caused mortality on wildlife.     

Differences in feeding ecology among three co-occurring species of wrasse (Teleostei: Labridae) on rocky reefs of temperate Australia

The foraging behaviours and dietary compositions of three co-occurring labrids (Ophthalmolepis lineolatus, Notolabrus gymnogenis and Pictilabrus laticlavius), which are conspicuous on rocky reefs in temperate south-eastern Australia, were investigated between 2003 and 2005. SCUBA observations at two locations showed that the feeding intensity, and hence the associated effects of these fishes on rocky reef invertebrate prey, was temporally consistent. Relative differences in the contributions of ingested prey and use of different feeding microhabitats demonstrated that the feeding ecology differed significantly among the three species. Thus, O. lineolatus fed on proportionately higher volumes of polychaetes, polyplacophorans, marginellid gastropods (especially Austroginella sp.), bivalves and echinoids, which were sighted opportunistically in a wide selection of microhabitats, but particularly in sand/rubble. Ambush hunting was used regularly by smaller N. gymnogenis and all sizes of P. laticlavius to forage on amphipods, small decapods and small gastropods at algal bases or fronds and Diopatra dentata tubes. Amphipods were similarly important in the diet of smaller O. lineolatus. Larger N. gymnogenis foraged opportunistically over an increased reef area and made greater use of microhabitats that offered minimal prey refuge (e.g. sand/rubble, bare rock/steel) from which common prey, in particular decapods, were obtained. The significant intra- and inter-specific differences in dietary compositions, allied with differences in the use of feeding microhabitats, would facilitate co-occurrence of these three conspicuous species and contribute to maintaining high richness of labrid species in reef systems. Echinoids were regularly consumed by each species but they made a moderate contribution to the diet of only O. lineolatus, which suggests that only one of the three labrids is likely to play a significant role in regulation of echinoid densities in these rocky reef habitats. However, the broad diets and diverse forging strategies employed by these labrid species imply that they have a system-wide influence on invertebrate prey on rocky reefs.     

Spatial variation of otolith elemental signatures among juvenile gray snapper (<Emphasis Type="Italic">Lutjanus griseus</Emphasis>) inhabiting southern Florida waters

Juvenile gray snapper, Lutjanus griseus, are believed to use bays and estuaries in southern Florida as nurseries before moving out to the adjoining reef tract as adults. Using high-resolution sector field-inductively coupled plasma-mass spectrometry (SF-ICP-MS), the elemental chemistry of the otoliths of juveniles from five nursery regions was resolved by establishing elemental “signatures” for each region. In this study we simultaneously analyzed 32 elements including a suite of rare earth elements. A stepwise variable selection procedure retained a subset of eight elements that contributed substantially to separating otolith samples, including two rare earth elements; this is one of the first studies in which rare earth elements in otoliths have contributed to separation of fish stocks. The classification success rate in assigning fishes to the correct region of origin was 82%. Resolution of sites less than 10 km apart suggested high site fidelity in juvenile gray snapper and little mixing of water masses between sites. The juvenile nursery signatures will be used to determine the relative contribution of different nurseries to the adult population on an adjoining reef tract.     

Invasive species impacts on ecosystem structure and function: A comparison of Oneida Lake, New York, USA, before and after zebra mussel invasion

Exotic species invasion is widely considered to affect ecosystem structure and function. Yet, few contemporary approaches can assess the effects of exotic species invasion at such an inclusive level. Our research presents one of the first attempts to examine the effects of an exotic species at the ecosystem level in a quantifiable manner. We used ecological network analysis (ENA) and a social network analysis (SNA) method called cohesion analysis to examine the effect of zebra mussel (Dreissena polymorpha) invasion on the Oneida Lake, New York, USA, food web. We used ENA to quantify ecosystem function through an analysis of food web carbon transfer that explicitly incorporated flow over all food web paths (direct and indirect). The cohesion analysis assessed ecosystem structure through an organization of food web members into subgroups of strongly interacting predators and prey. Our analysis detected effects of zebra mussel invasion throughout the entire Oneida Lake food web, including changes in trophic flow efficiency (i.e., carbon flow among trophic levels) and alterations of food web organization (i.e., paths of carbon flow) and ecosystem activity (i.e., total carbon flow). ENA indicated that zebra mussels altered food web function by shunting carbon from pelagic to benthic pathways, increasing dissipative flow loss, and decreasing ecosystem activity. SNA revealed the strength of zebra mussel perturbation as evidenced by a reorganization of food web subgroup structure, with a decrease in importance of pelagic pathways, a concomitant rise of benthic pathways, and a reorganization of interactions between top predator fish. Together, these analyses allowed for a holistic understanding of the effects of zebra mussel invasion on the Oneida Lake food web.     

Response of balanced network models to large-scale perturbation: Implications for evaluating the role of small pelagics in the Gulf of Maine

Exploring the response of an ecosystem, and subsequent tradeoffs among its biological community, to human perturbations remains a key challenge for the implementation of an ecosystem approaches to fisheries (EAF). To address this and related issues, we developed two network (or energy budget) models, Ecopath and Econetwrk, for the Gulf of Maine ecosystem. These models included 31 network “nodes” or biomass state variables across a broad range of trophic levels, with the present emphasis to particularly elucidate the role of small pelagics. After initial network balancing, various perturbation scenarios were evaluated to explore how potential changes to different fish, fisheries and lower trophic levels can affect model outputs. Categorically across all scenarios and interpretations thereof, there was minimal change at the second trophic levels and most of the “rebalancing” after a perturbation occurred via alteration of the diet matrix. Yet the model results from perturbations to a balanced energy budget fall into one of three categories. First, some model results were intuitive and in obvious agreement with established ecological and fishing theory. Second, some model results were counter-intuitive upon initial observation, seemingly contradictory to known ecological and fishing theory; but upon further examination the results were explainable given the constraints of an equilibrium energy budget. Finally, some results were counter-intuitive and difficult to reconcile with theory or further examination of equilibrium constraints. A detailed accounting of biomass flows for example scenarios explores some of the non-intuitive results more rigorously. Collectively these results imply a need to carefully track biomass flows and results of any given perturbation and to critically evaluate the conditions under which a new equilibrium is obtained for these types of models, which has implications for dynamic simulations based off of them. Given these caveats, the role of small pelagics as a prominent component of this ecosystem remains a robust conclusion. We discuss how one might use this approach in the context of further developing an EAF, recognizing that a more holistic, integrated perspective will be required as we continue to evaluate tradeoffs among marine biological communities.     

Flight initiation distance decreases during social activity in lizards (<Emphasis Type="Italic">Sceloporus virgatus</Emphasis>)

Flight initiation distance, the predator–prey distance when escape begins, is predicted by escape theory to decrease if fleeing entails loss of benefits. Shortening of flight initiation distance during social interactions is known only in males and only in a few species. In a previous study, male, but not female, Sceloporus virgatus lizards had shorter flight initiation distance when interacting with tethered conspecifics. Females in that study were not gravid or close to ovulating. I predicted that flight initiation distance would be shorter in gravid females that perform sidle-hopping displays to reject courtship than in lone females. I tested this prediction and examined effects of social interactions by males with free-ranging conspecifics to ensure that previous findings were not artifacts of tethering and experimental introduction of conspecifics. Flight initiation distance was shorter in females when interacting with males than when alone; it was also shorter in males interacting with either sex. Thus, when beneficial for reproductive reasons, social interaction affects flight initiation distance in females, but at other times, it does not. Lesser shortening of flight initiation distance in females than males may be a consequence of greater social benefit to males and protection of reproductive investment by females.