Biogeography of nonindigenous species: from description to prediction

Nonindigenous species are a major threat to the ecological integrity and biodiversity of marine and estuarine ecosystems. To become a successful invader, species must pass through four phases: (1) survive transport, (2) survive release, (3) establish a population, and (4) expand their range. To better understand these processes, an integrated framework was designed to capture life history characteristics, environmental preferences, dispersal mechanisms, and geographic distribution information for both native and nonindigenous marine and estuarine flora and fauna. Key aspects of this framework include: 1) consistent terminology; 2) translation of numerical habitat values and physiological requirements into classes; 3) development of classification schemas for natural history, environmental attributes, and geographic distributions; and 4) integration of biotic attributes to allow database queries on single or multiple species across spatial scales. Species data for the North Pacific were collected from the literature, local surveys, and regional databases. Ballast water discharges have been identified as a major source of species introductions. To predict the potential rate of invasion from ballast water, a linear invasion model predicting per capita invasion probabilities (PCIP) of new invaders was developed based on historic invasion rates and ballast discharge volumes for estuaries on the west coast of the United States. While the probability of invasion is likely to vary with ballast discharge values, organism concentrations in the ballast, and invasibility of individual ports, the PCIP provides a quantitative methodology for establishing protective ballast water discharge standards based on organism concentrations, the approach being used to regulate ballast water discharges both nationally and internationally. Habitat or niche models can be used to predict a nonindigenous species’ potential distribution in invaded areas over several spatial scales. The utility of non-parametric multiplicative regression (NPMR) was evaluated for predicting habitat- and estuary-scale distributions of native and nonindigenous species. Results indicate that NPMR generally performs well at both spatial scales and that distributions of nonindigenous species are predicted as well as those of native species. Development of approaches for regulating ballast water and identifying areas at risk through predictive modeling are useful tools in the management of the nonindigenous species threat

Ecoregional Analysis of Nearshore Sea-Surface Temperature in the North Pacific

The quantification and description of sea surface temperature (SST) is critically important because it can influence the distribution, migration, and invasion of marine species; furthermore, SSTs are expected to be affected by climate change. To better understand present temperature regimes, we assembled a 29-year nearshore time series of mean monthly SSTs along the North Pacific coastline using remotely-sensed satellite data collected with the Advanced Very High Resolution Radiometer (AVHRR) instrument. We then used the dataset to describe nearshore (<20 km offshore) SST patterns of 16 North Pacific ecoregions delineated by the Marine Ecoregions of the World (MEOW) hierarchical schema. Annual mean temperature varied from 3.8°C along the Kamchatka ecoregion to 24.8°C in the Cortezian ecoregion. There are smaller annual ranges and less variability in SST in the Northeast Pacific relative to the Northwest Pacific. Within the 16 ecoregions, 31-94% of the variance in SST is explained by the annual cycle, with the annual cycle explaining the least variation in the Northern California ecoregion and the most variation in the Yellow Sea ecoregion. Clustering on mean monthly SSTs of each ecoregion showed a clear break between the ecoregions within the Warm and Cold Temperate provinces of the MEOW schema, though several of the ecoregions contained within the provinces did not show a significant difference in mean seasonal temperature patterns. Comparison of these temperature patterns shared some similarities and differences with previous biogeographic classifications and the Large Marine Ecosystems (LMEs). Finally, we provide a web link to the processed data for use by other researchers

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

Ecoregional Analysis of Nearshore Sea-Surface Temperature in the North Pacific

The quantification and description of sea surface temperature (SST) is critically important because it can influence the distribution, migration, and invasion of marine species; furthermore, SSTs are expected to be affected by climate change. To better understand present temperature regimes, we assembled a 29-year nearshore time series of mean monthly SSTs along the North Pacific coastline using remotely-sensed satellite data collected with the Advanced Very High Resolution Radiometer (AVHRR) instrument. We then used the dataset to describe nearshore (<20 km offshore) SST patterns of 16 North Pacific ecoregions delineated by the Marine Ecoregions of the World (MEOW) hierarchical schema. Annual mean temperature varied from 3.8°C along the Kamchatka ecoregion to 24.8°C in the Cortezian ecoregion. There are smaller annual ranges and less variability in SST in the Northeast Pacific relative to the Northwest Pacific. Within the 16 ecoregions, 31–94% of the variance in SST is explained by the annual cycle, with the annual cycle explaining the least variation in the Northern California ecoregion and the most variation in the Yellow Sea ecoregion. Clustering on mean monthly SSTs of each ecoregion showed a clear break between the ecoregions within the Warm and Cold Temperate provinces of the MEOW schema, though several of the ecoregions contained within the provinces did not show a significant difference in mean seasonal temperature patterns. Comparison of these temperature patterns shared some similarities and differences with previous biogeographic classifications and the Large Marine Ecosystems (LMEs). Finally, we provide a web link to the processed data for use by other researchers

Monthly-mean SST in each of the Temperate North Pacific ecoregions based on a 29-year dataset.

<p>The horizontal axis represents months (e.g. 1 = January, 12 = December). The solid lines show the monthly-mean SST values. The dotted lines show the upper 95^th and lower 5^th quantiles of SST, which is a measure of within-month variation.</p

Hierarchical clustering dendrogram of 16 Temperate North Pacific ecoregions based on monthly-mean SST values.

<p>Clustering was performed with PRIMER <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030105#pone.0030105-Clarke1" target="_blank">[25]</a> using 3000 iterations in SIMPROF. Distances are Euclidean. Red, dotted branches indicate no significant difference between linked ecoregions. NEP = Northeast Pacific; NWP = Northwest Pacific.</p

Boundary comparison among the thermal patterns based on our SST cluster analysis, marine climates of Hall [<b>40</b>], SST clusters based on cluster analysis, and NOAA's Large Marine Ecosystems of the World (LMEs).

<p>The LMEs are denoted by the outer colored areas. Hall's marine climates are indicated by the dotted black lines, while the SST clusters derived by clustering MEOW ecoregions by SST are delineated by the inner colored outlines.</p

Temperate North Pacific realm, and the 16 MEOW ecoregions included in this paper.

<p>Major surface circulation pathways are labeled on the map and indicated with blue arrows, including the North Pacific Current (NPC), California Current System (CCS), North Equatorial Current (NEC), Kuroshio Current System (KCS), Kuroshio Extension (KE), Oyashio Current (OC), East Kamchatka Current (EKC).</p

Ecoregions plotted by maximum monthly versus minimum monthly-mean SST over the 29-year record.

<p>The y = x line indicates where minimum and maximum temperatures within an ecoregion are identical. Hence, proximity to the line indicates minimal variability in seasonal monthly SST. The Euclidean distances of 8.7 and 17 were obtained through clustering analysis. Solid lines connect ecoregions in order of latitude along the NEP and NWP.</p