Mark D. Sytsma

The role of containerships as transfer mechanisms of marine biofouling species

Fouling of ships is an important historical and enduring transfer mechanism of marine nonindigenous species (NIS). Although containerships have risen to the forefront of global maritime shipping since the 1950s, few studies have directly sampled fouling communities on their submerged surfaces, and little is known about differences in the fouling characteristics among commercial ship types. Twenty-two in-service containerships at the Port of Oakland (San Francisco Bay, California) were sampled to test the hypothesis that the extent and taxonomic richness of fouling would be low on this type of ship, resulting from relatively fast speeds and short port durations. The data showed that the extent of macroorganisms (invertebrates and algae) was indeed low, especially across the large surface areas of the hull. Less than 1% of the exposed hull was colonized for all apart from one vessel. These ships had submerged surface areas of >7000 m2, and fouling coverage on this area was estimated to be <l7 m2 per vessel, with zero biota detected on the hulls of many vessels. The outlying smaller vessel (4465 m2) had an estimated coverage of 90% on the hull and also differed substantially from the other ships in terms of its recent voyage history, shorter voyage range and slower speeds. Despite the low extent of fouling, taxonomic richness was high among vessels. Consistent with recent studies, a wide range of organisms were concentrated at more protected and heterogeneous (non-hull) niche areas, including rudders, stern tubes and intake gratings. Green algae and barnacles were most frequently sampled among vessels, but hydroids, bryozoans, bivalves and ascidians were also recorded. One vessel had 20 different species in its fouling assemblage, including non-native species (already established in San Francisco Bay) and mobile species that were not detected in visual surveys. In contrast to other studies, dry dock block areas did not support many organisms, despite little antifouling deterrence in some cases. Comparisons with previous studies suggest that the accumulation of fouling on containerships may be lower than on other ship types (eg bulkers and general cargo vessels), but more data are needed to determine the hierarchy of factors contributing to differences in the extent of macrofouling and non-native species vector risks within the commercial fleet.

Intra-coastal ballast water flux and the potential for secondary spread of non-native species on the US West Coast

Ballast water is a dominant mechanism for the interoceanic and transoceanic dispersal of aquatic non-native species (ANS), but few studies have addressed ANS transfers via smaller scale vessel movements. We analyzed ballast water reporting records and ANS occurrence data from four US West Coast port systems to examine patterns of intra-coastal ballast water transfer, and assess how ballast transfers may have influenced the secondary spread of ANS. In 2005, one third of the vessels arriving to the US West Coast originated at one of four West Coast port systems (intra-coastal traffic). These vessels transported and discharged 27% (5,987,588 MT) of the total ballast water volume discharged at these ports that year. The overlap of ANS (shared species) among port systems varied between 3% and 80%, with the largest overlap occurring between San Francisco Bay and LA/Long Beach. Our results suggest that intra-coastal ballast water needs further consideration as an invasion pathway, especially as efforts to promote short-sea shipping are being developed.

Distribution of the invasive New Zealand mudsnail ( Potamopyrgus antipodarum ) in the Columbia River Estuary and its first recorded occurrence in the diet of juvenile Chinook salmon ( Oncorhynchus tshawytscha )

Estuaries play an important role as nurseries and migration corridors for Chinook salmon and other fishes. The invasive New Zealand mudsnail, Potamopyrgus antipodarum (Gray, 1843), has been noted in the Columbia River Estuary and other estuaries in the western USA, yet no studies have addressed the estuarine impacts of this invader. Our data show P. antipodarum is currently found in five peripheral bays and many tributaries of the Columbia River Estuary, where it can constitute a major portion of the benthic invertebrate biomass and where it co-occurs with native amphipod species. We review the history of the P. antipodarum invasion in the Columbia River Estuary and discuss potential impacts on estuarine food webs. We also report the first occurrence of P. antipodarum in the diet of juvenile Chinook salmon from the Columbia River Estuary. Although present in Chinook diets at very low frequencies, our observations of P. antipodarum in Chinook gut contents may represent early stages of food web change due to the establishment of dense estuarine snail populations. Additional research is needed to determine the effects of P. antipodarum on benthic resources, native benthic invertebrates, and benthic predators. We encourage biologists working in western USA estuaries to be alert to the possibility of encountering P. antipodarum in benthic habitats and predator diets.

Comparison of the Genetic Structure of North and South American Populations of a Clonal Aquatic Plant

The dioecious plant Egeria densa Planchon (Hydrocharitaceae), indigenous to fresh water habitats in Brazil, Uruguay, and Argentina, has been introduced to many temperate habitats throughout the world where it propagates clonally and often becomes a serious weed. Representatives from populations in Oregon (USA) and southern Chile were tested for genetic variability by random amplified polymorphic DNA (RAPD) fingerprinting. Little genetic variability among samples was found despite the extreme geographical distance between the two introduced populations. These results suggest that similar bottlenecking events impacted both introductions or that there is low genetic diversity within the native source populations. Surveys of the genetic diversity of plants within the native range and more widespread and descriptive surveys of introduced populations are necessary to clarify the significance of the genetic similarity of these two widely separated populations.

Phenotypic plasticity of invasive Spartina densiflora (Poaceae) along a broad latitudinal gradient on the Pacific Coast of North America

PREMISE OF THE STUDY Phenotypic acclimation of individual plants and genetic differentiation by natural selection within invasive populations are two potential mechanisms that may confer fitness advantages and allow plants to cope with environmental variation. The invasion of Spartina densiflora across a wide latitudinal gradient from California (USA) to British Columbia (Canada) provides a natural model system to study the potential mechanisms underlying the response of invasive populations to substantial variation in climate and other environmental variables. METHODS We examined morphological and physiological leaf traits of Spartina densiflora plants in populations from invaded estuarine sites across broad latitudinal and climate gradients along the Pacific west coast of North America and in favorable conditions in a common garden experiment. KEY RESULTS Our results show that key foliar traits varied widely among populations. Most foliar traits measured in the field were lower than would be expected under ideal growing conditions. Photosynthetic pigment concentrations at higher latitudes were lower than those observed at lower latitudes. Greater leaf rolling, reduced leaf lengths, and lower chlorophyll and higher carbon concentrations were observed with anoxic sediments. Lower chlorophyll to carotenoids ratios and reduced nitrogen concentrations were correlated with sediment salinity. Our results suggest that the variations of foliar traits recorded in the field are a plastic phenotypic response that was not sustained under common garden conditions. CONCLUSIONS SPARTINA DENSIFLORA shows wide differences in its foliar traits in response to environmental heterogeneity in salt marshes, which appears to be the result of phenotypic plasticity rather than genetic differentiation.

Interrupting a Multi-Species Bioinvasion Vector: The Efficacy of In-Water Cleaning for Removing Biofouling on Obsolete Vessels

Vector management is the primary method for reducing and preventing nonindigenous species (NIS) invasions and their ecological and economic consequences. This study was the first to examine the efficacy of in-water scrubbing using a submersible cleaning and maintenance platform (SCAMP) to prevent invertebrate species transfers from a heavily fouled obsolete vessel. Initially, prior to treatment, 37 species were recorded in a biofouling matrix that reached 30cm depth in some locations. The bryozoan Conopeum chesapeakensis, and bivalves Mytilopsis leucophaeata and Ischadium recurvum, were dominant sessile species that created structure, supporting mobile biota that included crabs and the associated parasitic barnacle Loxothylacus panopae. Scrubbing had the effect of significantly reducing organism extent and the number of species per sample, but a substantial and diverse (30 species) residual fouling community remained across the entire vessel. Further assessments of management options are needed to prevent potentially damaging NIS transfers. Additional measures taken within an integrated vector management (IVM) strategy may further improve invasion prevention measures.

Potential Ocean Dispersal of Cordgrass (Spartina spp.) from Core Infestations

Abstract Nonnative Spartina species (cordgrasses) are widely distributed along the West Coast of North America, but have not invaded all bays with susceptible habitat. We used drift cards to assess the patterns and rates of potential Spartina propagule dispersal by ocean currents from estuaries with significant populations of one or more Spartina species. Cards were released monthly for 1 yr from Willapa Bay, Washington; Humboldt Bay, California; and San Francisco Bay, California; with recovery information reported by volunteers. Recovery rates averaged 37% for all release sites. Cards were commonly recovered close to their bay of release but were repeatedly found hundreds of kilometers both north and south of their release location. Cards most generally traveled northward from the release sites. Cards from Humboldt and Willapa bays were commonly recovered along the British Columbia coast, particularly in the winter. Cards released from Humboldt Bay were found farthest from their release sites. One card from Humboldt Bay traveled 2,800 km to Kodiak Island, Alaska. The timing of seed production, combined with prevailing currents, puts bays currently uninfested by Spartina at risk of repeated propagule loading by ocean currents. A coordinated coast-wide strategy for eradication of all nonnative Spartina will be critical to the success of individual bay-wide eradication efforts. Nomenclature: Common cordgrass, Spartina anglica C. E. Hubbard, dense-flowered cordgrass, Spartina densiflora Brongn., saltmeadow cordgrass, Spartina patens (Ait.) Muhl., smooth cordgrass, Spartina alterniflora Loisel Management Implications: Nonnative estuarine cordgrasses (Spartina spp.) are invasive weeds of saltmarshes and open mudflats in many bays and estuaries of North America, Australia, China, India, New Zealand, and numerous European countries. In North America the largest core infestations established along the Pacific Coast during the last 150 yr at Willapa Bay, Washington; Humboldt Bay, California; and San Francisco Bay, California. Estuarine plants such as Spartina can disperse to new bays when propagule-laden wrack mats consisting of senescent stems are washed out to the ocean and then drift with the currents. Understanding this natural dispersal mechanism is critical to the success of a coast-wide Spartina eradication strategy because there is a high likelihood of secondary spread from existing infestations—especially those with large historic propagule production. Indeed, a marked increase in novel satellite populations in the last 12 yr suggests spread to new habitats is increasing. This study provides the first examination of the dispersal potential for weedy plant species within the near-shore ocean environment from these three estuaries. The recovery patterns of drift cards, released monthly over the course of 1 yr underscore increased propagule loading at areas proximal to existing infestations, but also highlight the ability of ocean currents to carry seeds great distances, well within known propagule viability ranges. Drift card recoveries spanned 2,044 km north and south of Willapa Bay, 3,304 km north and south of Humboldt Bay, and 661 km north and south of San Francisco Bay. The scope of potential ocean dispersal presented here reinforces the need for effective eradication programs in propagule source areas of not only Spartina spp., but also other weeds that can disperse along this same pathway such as dwarf eelgrass (Zostera japonica), perennial pepperweed (Lepidium latifolium), and Algerian sea lavender (Limonium ramosissimum).

The potential for mitten crab Eriocheir sinensis H. Milne Edwards, 1853 (Crustacea: Brachyura) invasion of Pacific Northwest and Alaskan Estuaries.

Eriocheir sinensis H. Milne Edwards, 1853 is on the list of top 100 invaders compiled by the International Union for Conservation of Nature and Natural Resources. The recent establishment of a large Chinese mitten crab population in San Francisco Bay and the potential for introductions from California, Asia and Europe pose a significant invasion potential for estuaries and rivers from California to Alaska. This alien species would place at risk the catchment areas of the Pacific Northwest including the economic and social activities that depend upon intact aquatic systems. An analysis of ecological conditions that define the mitten crab’s native and introduced range suggests that large stable estuaries with long flushing times are necessary to sustain significant populations. Most Pacific Northwest estuaries have limited salinity intrusion, estuarine habitat and short flushing times and face a reduced risk of population establishment. Large, stable estuaries, such as the Puget Sound, may support significant populations. River-dominated estuaries, such as the Columbia River, have flushing times less than the duration of larval development and wouldn’t support populations. An application of a temperature based larval development rate to near-shore and estuary sea surface temperatures suggests that estuaries in Oregon and Washington have sufficient thermal regimes to support larval development. Most estuary systems in Alaska have limited periods where water temperatures are above the mortality threshold for the larval stages and are at a low risk for the establishment of populations. A potential sea temperature rise of two degrees Celsius would permit larval development in Alaskan estuaries, where sufficient estuarine and freshwater habitats exist.

Variation in tussock architecture of the invasive cordgrass Spartina densiflora along the Pacific Coast of North America

Some introduced species spread rapidly beyond their native range and into novel habitats mediated by a high degree of phenotypic plasticity and/or rapid evolutionary responses. In this context, clonality has been described as a significant factor contributing to invasiveness. We studied the abiotic environment and the responses of different tussock architecture traits of the invasive cordgrass Spartina densiflora Brongn. (Poaceae). A common garden experiment and field studies of S. densiflora in salt marshes across a wide latitudinal gradient from California (USA) to British Columbia (Canada) provided a model system for an integrated study of the potential mechanisms underlying the response of invasive S. densiflora populations to changes in environmental conditions. Our results showed that S. densiflora is able to adjust to widely variable climate (specifically, air temperature and the duration of the growing season) and sediment conditions (specifically, texture and hypoxia) through phenotypical plastic key functional tussock traits (e.g. shoot density, height, above- and below-ground biomass allocation patterns). Root biomass increased in coarser sediments in contrast to rhizomes, which were more abundant in finer sediments. Above-ground biomass and leaf area index increased mainly with air temperature during summer, and more robust (taller and wider) shoots were associated with more oxygenated sediments. In view of our results, S. densiflora appears to be a halophyte with a high degree of phenotypic plasticity that would enable it to respond successfully to changes in the abiotic conditions of salt marshes driven by global climate change, such as increasing salinity and temperatures.

Developing the Online Atlas of Oregon Lakes

In 2012, a team of researchers at Portland State University published the online Atlas of Oregon Lakes. The team included limnologists, cartographers, GIS specialists, and web map developers. This article describes the process from the print Atlas of Oregon Lakes, published by Oregon State University Press in 1985, to web mapping and digital publication of the online atlas in 2012. It also discusses the library-like issues of cataloging lakes, keeping on track with standards for scientific water data, and cooperating with other organizations.