Per capita invasion probabilities: an empirical model to predict rates of invasion via ballast water

Ballast water discharges are a major source of species introductions into marine and estuarine ecosystems. To mitigate the introduction of new invaders into these ecosystems, many agencies are proposing standards that establish upper concentration limits for organisms in ballast discharge. Ideally, ballast discharge standards will be biologically defensible and adequately protective of the marine environment. We propose a new technique, the per capita invasion probability (PCIP), for managers to quantitatively evaluate the relative risk of different concentration‐based ballast water discharge standards. PCIP represents the likelihood that a single discharged organism will become established as a new nonindigenous species. This value is calculated by dividing the total number of ballast water invaders per year by the total number of organisms discharged from ballast. Analysis was done at the coast‐wide scale for the Atlantic, Gulf, and Pacific coasts, as well as the Great Lakes, to reduce uncertainty due to secondary invasions between estuaries on a single coast. The PCIP metric is then used to predict the rate of new ballast‐associated invasions given various regulatory scenarios. Depending upon the assumptions used in the risk analysis, this approach predicts that approximately one new species will invade every 10–100 years with the International Maritime Organization (IMO) discharge standard of 50 μm per m³ of ballast. This approach resolves many of the limitations associated with other methods of establishing ecologically sound discharge standards, and it allows policy makers to use risk‐based methodologies to establish biologically defensible discharge standards.Keywords: Ballast water discharge, Propagule pressure, Aquatic invaders, Invasion probabilities, IMO standard

Topographic Control of Southern Ocean Gyres and the Antarctic Circumpolar Current: A Barotropic Perspective

In the Southern Ocean the Antarctic Circumpolar Current is significantly steered by large topographic features, and sub-polar gyres form in their lee. The geometry of topographic features in the Southern Ocean is highly variable, but the influence of this variation on the large-scale flow is poorly understood. Using idealised barotropic simulations of a zonal channel with a meridional ridge, it is found that the ridge geometry is important for determining the net zonal volume transport. A relationship is observed between ridge width and volume transport that is determined by the form stress generated by the ridge. Gyre formation is also highly reliant on the ridge geometry. A steep ridge allows gyres to form within regions of unblocked geostophic ( f /H) contours, with an increase in gyre strength as the ridge width is reduced. These relationships between ridge width, gyre strength, and net zonal volume transport emerge in order to simultaneously satisfy the conservation of momentum and vorticity

Diversity and patterns of marine non-native species in the archipelagos of Macaronesia

Tiago Marques and Carolina Marques thank partial support by CEAUL (funded by FCT through the project UIDB/00006/2020).Aims The present study is the first attempt to grasp the scale and richness of marine biological invasions in Macaronesia. We pioneered a comprehensive non-native species (NNS), inventory in the region to determine their diversity patterns and native distribution origins. NNS were defined here as the result of both introductions and range expansions. We also used statistical modelling to examine relationships among NNS richness, anthropogenic activities, demographic and geographical variables across Macaronesia. Location Macaronesia. Methods A comprehensive literature search was conducted for marine NNS records in Macaronesia, registering the first record's location and year from 1884 to 2020. We used univariate and multivariate analyses to evaluate differences and similarities in community composition. By applying a Generalized Linear Model (GLM), we tested hypotheses regarding NNS richness as a function of anthropogenic activities, demographic and geographical variables. Results A total of 144 marine non-native species (NNS) were recorded for the whole of Macaronesia. The highest NNS richness was registered in the Canary Islands (76 NNS), followed by the Azores (66 NNS), Madeira (59 NNS) and finally Cabo Verde (18 NNS). Some differences amongst archipelagos were observed, such as the high number of non-native macroalgae in the Azores, fishes in the Canary Islands and tunicates in Cabo Verde. Overall, macroalgae, tunicates and bryozoans were the predominant taxonomic groups in the Macaronesian archipelagos. Madeira and Canary Islands were the archipelagos with more similarity in marine NNS, and Cabo Verde the most divergent. Finally, GLM suggested that non-native richness patterns across Macaronesia were dependent on the considered archipelago and strongly affected by (1) minimum distance to the mainland, (2) the total number of ports and marinas and (3) total marinas area (km2). Conclusions The model results and NNS listing in the present study will likely raise the awareness and response regarding marine NNS in the whole Macaronesia region, serving as a baseline for future research as well as implementing and enforcing regulations related to the introduction of marine NNS in oceanic islands.Publisher PDFPeer reviewe

Collapse of the North American ice saddle 14,500 years ago caused widespread cooling and reduced ocean overturning circulation

Collapse of ice sheets can cause significant sea level rise and widespread climate change. We examine the climatic response to meltwater generated by the collapse of the Cordilleran-Laurentide ice saddle (North America) ~14.5 thousand years ago (ka) using a high-resolution drainage model coupled to an ocean-atmosphere-vegetation general circulation model. Equivalent to 7.26 m global mean sea level rise in 340 years, the meltwater caused a 6 sverdrup weakening of Atlantic Meridional Overturning Circulation (AMOC) and widespread Northern Hemisphere cooling of 1–5°C. The greatest cooling is in the Atlantic sector high latitudes during Boreal winter (by 5–10°C), but there is also strong summer warming of 1–3°C over eastern North America. Following recent suggestions that the saddle collapse was triggered by the Bølling warming event at ~14.7–14.5 ka, we conclude that this robust submillennial mechanism may have initiated the end of the warming and/or the Older Dryas cooling through a forced AMOC weakening

The Effects of Copper Pollution on Fouling Assemblage Diversity: A Tropical-Temperate Comparison

BACKGROUND: The invasion of habitats by non-indigenous species (NIS) occurs at a global scale and can generate significant ecological, evolutionary, economic and social consequences. Estuarine and coastal ecosystems are particularly vulnerable to pollution from numerous sources due to years of human-induced degradation and shipping. Pollution is considered as a class of disturbance with anthropogenic roots and recent studies have concluded that high frequencies of disturbance may facilitate invasions by increasing the availability of resources. METHODOLOGY/PRINCIPAL FINDINGS: To examine the effects of heavy metal pollution as disturbance in shaping patterns of exotic versus native diversity in marine fouling communities we exposed fouling communities to different concentrations of copper in one temperate (Virginia) and one tropical (Panama) region. Diversity was categorized as total, native and non-indigenous and we also incorporated taxonomic and functional richness. Our findings indicate that total fouling diversity decreased with increasing copper pollution, whether taxonomic or functional diversity is considered. Both native and non-indigenous richness decreased with increasing copper concentrations at the tropical site whereas at the temperate site, non-indigenous richness was too low to detect any effect. CONCLUSIONS/SIGNIFICANCE: Non-indigenous richness decreased with increasing metal concentrations, contradicting previous investigations that evaluate the influence of heavy metal pollution on diversity and invasibility of fouling assemblages. These results provide first insights on how the invasive species pool in a certain region may play a key role in the disturbance vs. non-indigenous diversity relationship

On the mechanics of lake circulation

Four aspects of the problem of describing the phenomena governing the flow pattern in a lake are investigated with the aid of simple mathematical models. Analogies are pointed out between the two-dimensional models and the corresponding problems in the elastic deformation of thin rigid plates. A. The dependence of the flow pattern in a longitudinal vertical cross-section of a lake on a given temperature distribution within the lake is studied with the aid of a two-dimensional lake model of semicircular vertical cross-section. A stream function satisfying the two-dimensional non-homogeneous biharmonic equation is introduced. Solutions are found consisting of a through flow function having a source and sink at the ends of the diameter plus a circulation function which is obtained in terms of a Green's function and the horizontal density gradient. The total stream function satisfies the conditions of no slipping at a solid boundary and zero stress at a free surface. Two cases of simple density structure are considered, and streamlines are drawn for several ratios of circulation to through flow. B. The departure of the lake surface from the horizontal required to maintain a pressure head sufficient to overcome eddy viscosity is estimated by considering the pressure distribution in the case of the through flow function introduced above. C. The effect of Coriolis forces on the flow in a canal is investigated with the aid of a three-dimensional semi-oylindrical model. It is shown that the effect on the shape of the canal surface is negligible. For a sufficiently low value of vertical density stratification the effect of Coriolis forces may show up in the tilting of constant density surfaces. D. The effect of wind stress on circulation in a vertical lake cross-section is investigated mathematically with the aid of a two-dimensional model. The results are found to agree quite closely with experiments on the deformation of a semicircular plate recently reported in the literature.Science, Faculty ofPhysics and Astronomy, Department ofGraduat

Data from: Exploring potential establishment of marine rafting species after transoceanic long-distance dispersal

Aim On March 11, 2011, the Great East Japan Earthquake triggered a massive tsunami that resulted in the largest known rafting event in recorded history. By spring 2012, marine debris began washing ashore along the Pacific Coast of the U.S. and Canada with a wide-range of Asian coastal species attached. We used this unique dataset, where the source region, date of dislodgment, and landing location are known, to assess the potential for species invasions by transoceanic rafting on marine debris. Location Northeast Pacific from 20 to 60°N Time period Current Major taxa studied Forty-eight invertebrate and algal species recorded on Japanese tsunami marine debris. Methods We developed Maximum Entropy (MaxEnt) species distribution models for 48 species recorded on Japanese tsunami marine debris to predict establishment potential along the Pacific Coast from 20-60°N. Models were compared within the context of historical marine introductions from Japan to this region to validate the emergence of marine debris as a novel vector for species transfer. Results Overall, 27% (13 species) landed with debris at locations with suitable environmental conditions for establishment and survival, indicating that these species may be able to establish new populations or introduce greater genetic diversity to already established non-native populations. A further 22 species have environmental match in areas where tsunami debris likely landed, but was not extensively sampled. Nearly 100 Japanese marine species previously invaded the northeastern Pacific, demonstrating this region's environmental suitability for rafting Japanese biota. Historical invasions from Asia are highest in California and largely known from bays and harbors. Main conclusions Marine debris is a novel and growing vector for non-native species introduction. By utilizing a unique dataset of Japanese tsunami marine debris species, our predictive models show capacity for new transoceanic invasions and can focus monitoring priorities to detect successful long-distance dispersal across the world’s oceans