Invasion Expansion: Time since introduction best predicts global ranges of marine invaders.

Strategies for managing biological invasions are often based on the premise that characteristics of invading species and the invaded environment are key predictors of the invader's distribution. Yet, for either biological traits or environmental characteristics to explain distribution, adequate time must have elapsed for species to spread to all potential habitats. We compiled and analyzed a database of natural history and ecological traits of 138 coastal marine invertebrate species, the environmental conditions at sites to which they have been introduced, and their date of first introduction. We found that time since introduction explained the largest fraction (20%) of the variability in non-native range size, while traits of the species and environmental variables had significant, but minimal, influence on non-native range size. The positive relationship between time since introduction and range size indicates that non-native marine invertebrate species are not at equilibrium and are still spreading, posing a major challenge for management of coastal ecosystems

Multiple novel prostate cancer susceptibility signals identified by fine-mapping of known risk loci among Europeans

Genome-wide association studies (GWAS) have identified numerous common prostate cancer (PrCa) susceptibility loci. We have fine-mapped 64 GWAS regions known at the conclusion of the iCOGS study using large-scale genotyping and imputation in 25 723 PrCa cases and 26 274 controls of European ancestry. We detected evidence for multiple independent signals at 16 regions, 12 of which contained additional newly identified significant associations. A single signal comprising a spectrum of correlated variation was observed at 39 regions; 35 of which are now described by a novel more significantly associated lead SNP, while the originally reported variant remained as the lead SNP only in 4 regions. We also confirmed two association signals in Europeans that had been previously reported only in East-Asian GWAS. Based on statistical evidence and linkage disequilibrium (LD) structure, we have curated and narrowed down the list of the most likely candidate causal variants for each region. Functional annotation using data from ENCODE filtered for PrCa cell lines and eQTL analysis demonstrated significant enrichment for overlap with bio-features within this set. By incorporating the novel risk variants identified here alongside the refined data for existing association signals, we estimate that these loci now explain ∼38.9% of the familial relative risk of PrCa, an 8.9% improvement over the previously reported GWAS tag SNPs. This suggests that a significant fraction of the heritability of PrCa may have been hidden during the discovery phase of GWAS, in particular due to the presence of multiple independent signals within the same regio

Disturbance-related heterogeneity in the seed banks of a marine angiosperm

1 Patterns in the distribution of seeds of the marine angiosperm Halodule uninervis were described over spatial scales ranging from a few centimetres to meadows separated by more than 120 km along the north-eastern coast of Queensland, Australia. Separate surveys examined how seed bank densities were related to: (i) the distribution of male and female plants (primary dispersal) and (ii) disturbances caused by turbulent water movement and the foraging of large marine vertebrates.\ud \ud 2 The distribution of seeds was extremely heterogeneous at very small scales of sampling (centimetres to tens of centimetres). Variation in seed abundance within individual meadows (87% of total variation in seed densities) was at least an order of magnitude greater than that among separate intertidal populations (13%). Densities of seeds were greatest in micro-topographic depressions where the overlying vegetation had been removed by directional water currents and the feeding activities of dugongs. Smaller disturbances that did not disrupt the cover of vegetation had no effect on seed abundance. Detailed mapping of the distributions of seeds and male and female reproductive shoots showed only a weak relationship between primary seed production and the seed bank, but revealed a pattern of seed distribution that was consistent with accumulation in linear depressions in the meadow.\ud \ud 3 The seed banks of intertidal sediments exhibit many similarities to those of physically dynamic desert sands. In these unstable environments, seeds are most abundant in sheltered micro-habitats where sediment mobility is impeded. Plants that inhabit desert and marine sands appear to have responded similarly to strong selective pressures on seedling recruitment by developing mechanisms that restrict primary seed dispersal to take advantage of micro-sites provided by established plants

Boat harbour design can exacerbate hull fouling

Hull fouling is a major cost for owners of small vessels and an important pathway for the spread of non-indigenous aquatic species. The extent of fouling depends on a hull's susceptibility to recruitment by aquatic organisms and the local availability of competent planktonic propagules (‘propagule pressure’). Management strategies have typically been concerned with increasing resistance of the hull to recruitment through the use of toxic paints. Here we tested the hypothesis that fouling is influenced by the design of the harbour in which the boat is moored. We compared recruitment of sessile invertebrates to available surfaces in two types of recreational boat harbours: marinas that were partially enclosed by a permanent breakwall, and marinas that lacked breakwalls. Recruitment in the marinas was compared to coastal reference sites that were not used for mooring. At each location, recruitment tiles were deployed for 4 weeks on four separate occasions over a period of 2 years. Measurements of current velocities and spatial patterns of water flow at each location showed that permanent breakwalls created complex patterns of circulation that retained water within the marina basin for up to 12 h d−1. Despite large regional and temporal variability in fouling over time, most organisms recruited in greatest numbers to surfaces in partially enclosed marinas, and were often several orders of magnitude more abundant in the enclosed marinas than in unenclosed marinas or coastal reference locations. Harbour design has an important influence on the rate at which fouling organisms recruit to available surfaces within marinas. Entrainment of water in enclosed marinas may limit the dispersal of planktonic propagules by advective currents but effectively increases propagule pressure to available surfaces, including resident boat hulls. This is likely to accelerate the development of hull-fouling assemblages and increase the chances of transport of non-indigenous species that establish populations in the harbour basin

Methods for assessing seagrass seed ecology and population genetics

Ecological populations result from processes that affect the birth, growth, survival and interaction of genetic individuals (genets). In seagrasses and other flowering plants, the recruitment of new genets occurs through the production and germination of seeds. Seeds variously provide a means by which plants disperse to new locations, recover from catastrophic disturbances, or survive unfavourable periods for growth. They are, therefore, an important demographic stage in plant populations. Study of the recruitment and survival of genets in seagrass populations is complicated by the difficulty in distinguishing one genet from another. The clonal growth aspect of seagrasses means that a meadow could be comprised of just a single, large individual or many smaller, intermingled genets. Knowledge of the number and distribution of genets is important for understanding the pattern of flowering and seed production. For example, seed production may vary greatly among separate meadows of the same species, as well as within meadows, because differences in the size and spatial arrangement of genets affect rates of pollination and genetic exchange (Figure6-1). Interspecific differences in reproductive effort can also have a basis in local population structure, as species with potentially long-lived plants (e.g., Posidonia) are likely to form larger genets and might be expected to invest fewer resources into annual seed production than shorter-lived species (e.g., Halophila). For these reasons, studies of the genetic structure of seagrass meadows and their reproductive ecology are intimately linked. By relating the genetic composition of meadows to their reproductive behaviour we may begin to determine the effective size and spatial extent of seagrass populations and the processes by which they are established and maintained. In this chapter we review some of the methods that can be applied to study the seed ecology and genetic structure of seagrass meadows

“Take only photographs and leave only footprints”?: An experimental study of the impacts of underwater photographers on coral reef dive sites\ud

Impacts caused by recreational scuba diving on coralreefs vary widely among different dive locations and individual divers. Linear modelling was used to explore a range of individual and situational risk factors associated with divers who damaged corals in the Great Barrier Reef Marine Park. Recreational divers were followed for 10–15 min, and all contacts with, and damage to corals were recorded. Information on the divesite, diving experience, gender, and use of an underwater camera were recorded. Thirty-two out of 214 divers (15%) damaged or broke corals, mostly by fin kicks (95%). Impacts were most likely to be caused by male divers, in the first 10 min of the dive, at sites with a large abundance of branching corals. Specialist underwaterphotographers caused more damage on average (1.6 breaks per 10 min) than divers without cameras (0.3 breaks per 10 min). To explore the effects of gender and use of a camera further, we issued single-use underwater cameras to 31 randomly chosen divers and compared their behaviour to a control group. Use of a camera had no influence on the rate or amount of damage caused by these naive photographers, but male divers were more likely to break corals and caused significantly more damage, on average, (1.4 breaks per 15 min) than female divers (0.3 breaks per 15 min). Variability in the amount of damage caused by divers in our sample reflected the very different underwater behaviours exhibited by specialist and non-specialist photographers, and male and female divers. Greater understanding of the causes of harmful behaviours by these groups will allow better targeting of on-site interpretative and cautionary information and may prove to be a more palatable management strategy than regulation of site use

Evidence for systemic changes in the benthic fauna of tropical estuaries as a result of urbanization

The effects of urban development cause substantial physical changes in coastal waterways through hardening and reclamation of river banks, alteration of water flow, and diffuse and point-source discharges of pollutants. The cumulative effects of urbanization on the fauna of estuaries are not well understood. This study examined the benthic infauna of two urban and three rural estuaries near Townsville, North Queensland. A range of univariate and multivariate statistics was used to relate variation in the benthic assemblages to concentrations of contaminants (heavy metals and hydrocarbons) within the sediments of each estuary. Sediments in the most developed estuary contained concentrations of heavy metals and petroleum hydrocarbons that were several orders of magnitude greater than those from non-urban waterways. The fauna at these sites was dominated by cirratulid and sternaspid polychaetes and lacked filter-feeding bivalves and other molluscs that were common in less developed estuaries. These differences were generally consistent throughout each estuary, indicating estuary-wide patterns of change, that were most strongly associated with spatial patterns in the distribution of Pb, Cu and hydrocarbons

A risk-based predictive tool to prevent accidental introductions of nonindigenous marine species

Preventing the introduction of nonindigenous species (NIS) is the most efficient way to avoid the costs and impacts of biological invasions. The transport of fouling species on ship hulls is an important vector for the introduction of marine NIS. We use quantitative risk screening techniques to develop a predictive tool of the abundance and variety of organisms being transported by ocean-going yachts. We developed and calibrated an ordinal rank scale of the abundance of fouling assemblages on the hulls of international yacht hulls arriving in New Zealand. Fouling ranks were allocated to 783 international yachts that arrived in New Zealand between 2002 and 2004. Classification tree analysis was used to identify relationships between the fouling ranks and predictor variables that described the maintenance and travel history of the yachts. The fouling ranks provided reliable indications of the actual abundance and variety of fouling assemblages on the yachts and identified most (60%) yachts that had fouling on their hulls. However, classification tree models explained comparatively little of the variation in the distribution of fouling ranks (22.1%), had high misclassification rates (∼43%), and low predictive power. In agreement with other studies, the best model selected the age of the toxic antifouling paint on yacht hulls as the principal risk factor for hull fouling. Our study shows that the transport probability of fouling organisms is the result of a complex suite of interacting factors and that large sample sizes will be needed for calibration of robust risk models

Effects of self-guided snorkeling trails on corals in a tropical marine park

Underwater trails are intended as interpretative tools in marine parks, but concentrating divers and snorkelers in defined areas may negatively affect the surrounding environment. We examined spatial and temporal patterns in the effects of use of underwater trails on coral reef flats in the Great Barrier Reef Marine Park, Australia. Changes in benthic assemblages were assessed on two new trails used by snorkelers, two unused (control) trails, and two undisturbed areas. Total percent coral cover, numbers of broken colonies, and living coral fragments were counted 6 months before and 6 months after the new trails began to be used. Spatial patterns of effects around concentrated nodes of use were determined by stratified sampling around and away from the interpretative signs within each trail. Despite comparatively low levels of use (approximately 15 snorkelers per trail per week), snorkelers caused significant damage to corals along the trails. Branching corals (non-Acropora branching corals and Millepora spp.) were most affected. More damage occurred near the interpretative signs than elsewhere on the trails. The numbers of broken branches and damaged coral colonies in the snorkeling trails increased rapidly but stabilized within 2 months of the commencement of use. There was no significant change in overall benthic assemblages within the trails after 6 months of use by snorkelers. Although concentrating snorkelers within confined trails caused increased damage to corals, the effects can be mitigated by appropriate design and placement of the trails and by managing the behaviour of snorkelers. Interpretative information should warn users about the damage they may cause when swimming along the trails. Managing the behaviour of snorkelers in the water is likely to be more effective in reducing damage than simply applying fixed limits to the amount of use the trails receive

Crowding norms in marine settings: A case study of snorkeling on the Great Barrier Reef

Research on crowding in natural environments has traditionally been concerned with encounters in terrestrial settings. Increased visitation to tropical marine environments, however, has meant that evaluations of aesthetic quality are increasingly becoming issues for managers of marine parks. In this study, we used image-capture techniques to develop a series of above- and below-water images depicting different numbers of people snorkeling in a coral reef setting. The presence of safety facilities in the above-water settings was manipulated to examine the influence of human-made structures on perception of crowding. Four respondent groups—a scuba-diving club, local residents, tourists, and US university students—representing different levels of experience in marine recreation on the Great Barrier Reef, were asked to rate the acceptability of each image. Ratings were significantly influenced by the number of people in the images, the prior experience and gender of the respondents, and the presence of safety infrastructure. Experienced scuba divers preferred scenes without people or infrastructure, while novices regarded the presence of both as more acceptable. The results suggest that evaluations of social density and crowding may vary between below-water scenes and the more familiar abovewater setting. A lack of concordance between how respondents rated the images and their nominated preferences for the number of other people in the settings highlights a need for more research on how perceptions of resource conditions should be measured in marine environments