Evangelina Schwindt

No longer the pristine confines of the world ocean: a survey of exotic marine species in the southwestern Atlantic

We conducted a comprehensive survey of existing knowledge about exotic marine organisms introduced to the southwestern Atlantic Ocean, including coastal and shelf areas of Uruguay and Argentina. This domain is equivalent to the so-called Patagonian Shelf Large Marine Ecosystem, and corresponds to two biogeographic provinces: warm-temperate (Argentine Province) and cold temperate (Magellanic Province). The search included species that can be confidently categorized as introduced (31) and cryptogenic species (46). We present a comprehensive picture of recorded introductions (the first for this region) and some prominent ecological consequences. Most coastal ecosystems between the La Plata River estuary and central Patagonia have already been modified, or are expected to be so in the short term. Five recent, human-mediated biological invasions have already had a significant ecological impact. A barnacle (Balanus glandula) belt has developed on all rocky shores where none was present 30 years ago, a macro-fouler (Limnoperna fortunei) and a reef-builder (Ficopomatus enigmaticus) have strongly modified estuarine ecosystems, Pacific oyster (Crassostrea gigas) reefs are expanding in shallow bays at a fast rate, and kelp (Undaria pinnatifida) is rapidly modifying nearshore benthic communities along the coasts of central Patagonia. At this point, it is uncertain how many of the cordgrasses (Spartina spp.) found in coastal salt marshes correspond to exotic forms. Only exposed sandy beaches appear to be free from the pervasive ecological impact of invasion by exotic species. Poor knowledge of the regional biota makes it difficult to track invasions.

Rapid Assessment Survey for exotic organisms in southern California bays and harbors, and abundance in port and non-port areas

In recent decades, the world has witnessed an array of harmful invasions by exotic marine organisms. To provide the public and policymakers with better information on the status of exotic species in southern California waters, and to assess differences between port and non-port areas, a Rapid Assessment Survey of selected habitat types in sheltered waters between San Diego and Oxnard was conducted in the summer of 2000. The objectives included comparing the prevalence of exotic species among habitats and regions and between recent and past surveys; obtaining reference data for future assessments of changes in invasion status and the effectiveness of prevention or control efforts; detecting new invasions; and documenting significant range extensions. Twenty-two sites were sampled to include the three major commercial port areas in southern California, non-port-area marinas and lagoon sites. Sampling included dock fouling and adjacent soft-bottom benthos, nearby intertidal sites, and selected subtidal lagoon habitats. Samples were collected by a variety of manual techniques. Sixty-nine of the species collected are exotic, including representatives from two algal divisions and six invertebrate phyla. Ascidians are especially well-represented (14 exotic species) and widely occurring, and some bivalves and bryozoans also occur very widely. The numbers and proportions of exotic taxa were not significantly greater in port areas than in non-port areas.

A Characterization of Patagonian Salt Marshes

We combined literature reviews with an analysis of regional cartography, aerial photographs, and satellite images to identify the locations of heretofore-unknown salt marshes along the Patagonian coastline of Argentina. Subsequent ground surveys confirmed the presence of the marshes. While numerous sites still require verification, our surveys confirmed the existence of 27 large coastal salt marshes, which had estimated areas of between 3 and 2400 ha distributed along ∼225 km of coastline. We described the major patterns of landscape physiognomy and community structure at eight of these sites. We classified these marshes as either muddy or rocky marshes, and subdivided them into Spartina and Sarcocornia marshes depending on the dominant vegetation. Muddy marshes were the most common type and showed a clear regional pattern with Spartina-dominated communities in the north (≤ 42°S) and Sarcocornia-dominated systems in the south (≥ 42°S). Plant height and standing crop biomass tended to be lower at higher latitudes, but plant cover showed the opposite trend. Spartina marshes had a more diverse marine macro-invertebrate fauna than Sarcocornia marshes, when the two marsh types occur at similar latitudes. Although the diversity of invertebrates was relatively low along the entire latitudinal range, most marshes supported unique species assemblages.

The invasion of the acorn barnacle Balanus glandula in the south-western Atlantic 40 years later

The acorn barnacle Balanus glandula (Darwin 1854) is native to the Pacific coast of North America and was accidentally introduced in Argentina in the early 1970s. Here the invasion status of this species is reviewed in the south-western Atlantic focusing on geographical patterns of density, cover, biomass, size and recruitment, and also estimating its rate of spread. Field surveys along rocky shores and a literature review show that B. glandula invaded most of the rocky shores of Argentina at a high rate of spread. Density and cover of barnacles do not follow a latitudinal trend; instead both variables show a bimodal pattern with the highest values in two distant locations (Puerto Lobos and Bahia Bustamante). However, the size of the barnacles increases with latitude, and is positively related to biomass. Recruitment of this species varies between wave exposed and protected areas, and over time. At lower latitudes barnacles recruit in winter, while at higher latitudes they recruit in spring and summer. The differences observed in density and recruitment suggest that along the Argentinean coast, oceanographic processes have a stronger influence in the distribution and success of the barnacles than the gradient in wave exposure. Balanus glandula is a successful invader which has completely re-shaped the native intertidal landscape. Moreover, considering the wide temperature range that this barnacle tolerates in native and invaded regions, the entire coastline of South America could be colonized by this species in the future.

Global environmental changes: setting priorities for Latin American coastal habitats

As the effects of the Global Climate Changes on the costal regions of Central and South Americas advance, there is proportionally little research being made to understand such impacts. This commentary puts forward a series of propositions of strategies to improve performance of Central and South American science and policy making in order to cope with the future impacts of the Global Climate Changes in their coastal habitats.

Habitat complexity and community composition: relationships between different ecosystem engineers and the associated macroinvertebrate assemblages

Several species of ecosystem engineers inhabiting coastal environments have been reported structuring different kinds of communities. The magnitude of this influence often depends on the habitat complexity introduced by the engineers. It is commonly accepted that an increase in habitat complexity will result in an increase in diversity and/or abundance in the associated fauna. The rocky salt marshes along the coast of Patagonia are dominated by cordgrasses, mussels, and barnacles forming a mosaic of engineered habitats with different complexity. This system allows us to address the following questions: how different is a macroinvertebrate assemblage when dominated by different ecosystem engineers? And, is there a positive relationship between increasing habitat complexity and the species richness, diversity and total density of the assemblages? To address these questions, we compared the three ecological scenarios with decreasing habitat complexity: cordgrass–mussel, mussel, and barnacle-engineered habitats. We found a total of 22 taxa mostly crustaceans and polychaetes common to all scenarios. The three engineered habitats showed different macroinvertebrate assemblages, mainly due to differences in individual abundances of some taxa. The cryptogenic amphipod Orchestia gammarella was found strictly associated with the cordgrass–mussel habitat. Species richness and diversity were positively related with habitat complexity while total density showed the opposite trend. Our study suggests that species vary their relative distribution and abundances in response to different habitat complexity. Nevertheless, the direction (i.e., neutral, positive or negative) and intensity of the community’s response seem to depend on the physiological requirements of the different species and their efficiency to readjust their local spatial distribution in the short term.

What would Darwin have written now

We often wonder how many of the pristine places left on Earth we can protect from deterioration before it is too late. The assumption that remote regions remain pristine plays a key role in directing policies for regional environmental management and conservation, and affects the local and global financial impetus to do so. In this paper, we use Argentinean Patagonia and the SW Atlantic as examples to argue that the assumption ‘remote region = pristine region’ is unjustified and based on a lack of information rather than on scientific evidence. We also discuss the major existing environmental threats to this supposedly ‘pristine’ region, and use emblematic examples to provide a more realistic picture of the regional environmental integrity and to set recommendations directed to improve environmental management and conservation within this context.

First record of the invasive red alga Polysiphonia morrowii Harvey (Rhodomelaceae, Rhodophyta) on the Patagonian shores of the Southwestern Atlantic.

Abstract Seaweed invasions are recognized as one of the major threats to biological diversity and coastal resources. Nevertheless, the number of introduced macroalgae has been underestimated due to the increasing number of cryptic invasions. Polysiphonia morrowii is native to the North Pacific and several cryptic introductions of this species have been reported over the past decade. In this study, we recorded the presence of the invasive P. morrowii in the Southwestern Atlantic (Patagonia Argentina) using a morphological and molecular approach for the identification at species level. Polysiphonia morrowii specimens from Argentina showed no morphological differences from members of invasive populations in France. We found two different haplotypes, suggesting that P. morrowii was probably introduced into this area by multiple introduction events. The increasing number of shipping and aquaculture activities worldwide and the ability of this species to be a successful invader suggest that P. morrowii is likely to be a cosmopolitan invasive species and that further management planning is required for its early detection and control.

Ecological impacts of the austral-most population of Crassostrea gigas in South America: a matter of time?

Abstract The Pacific oyster Crassostrea gigas is one of the most invasive species worldwide. This oyster has a preponderant ecological role in the invaded environments, for example structuring the benthic community through the provision of micro-habitats. Twenty-five years after its introduction in Argentina, the species is colonizing new areas along the coast, extending northwards and southwards its local distribution. In this study, we provide the first ecological characterization of the southern-most population of C. gigas; where the composition, density, richness and diversity of the macroinvertebrate assemblages associated with zones with oysters were compared with zones where it is absent at four different times of the year. Additionally, the main epibionts taxa settled on the oyster shells were studied. Our results showed differences in the assemblage composition between zones. However, these differences were not consistent throughout the year. Furthermore, density, richness and diversity were higher in the zones with oysters only in one of the surveys and the parameters did not differ between zones in the remaining months. Moreover, the majority of oysters were used as settlement substrate by the sessile common species present in the area. Thus, our work provides new information about the ecology of C. gigas in recently invaded areas that enhance our understanding of the role that facilitation plays in physically stressful ecosystems and the importance that density and time since the invasion may have in the engineering effects of the species.

Differential benthic community response to increased habitat complexity mediated by an invasive barnacle

Invasive species threaten native ecosystems worldwide. However, these species can interact positively with local communities, increasing their richness, or the abundance of some species. Many invasive species are capable of influencing the habitat itself, by ameliorating physical stress and facilitating the colonization and survival of other organisms. Barnacles are common engineer species that can change the physical structure of the environment, its complexity, and heterogeneity through their own structure. Balanus glandula is a native barnacle of the rocky shores of the west coast of North America. In Argentina, this invasive species not only colonizes rocky shores but it also has successfully colonized soft-bottom salt marshes, where hard substrata are a limiting resource. In these environments, barnacles form three-dimensional structures that increase the structural complexity of the invaded salt marshes. In this work, we compared the composition, density, richness, and diversity of the macroinvertebrate assemblages associated with habitats of different structural complexity in two Patagonian salt marshes where B. glandula is well established. Our results showed differences in the relative distribution and abundances of the invertebrate species between habitats of different complexities. Furthermore, the response of the communities to the changes in the structural complexity generated by B. glandula was different in the two marshes studied. This highlights the fact that B. glandula facilitates other invertebrates and affect community structure, mainly where the settlement substrata (Spartina vs. mussels) are not functionally similar to the barnacle. Thus, our work shows that the rocky shore B. glandula is currently a critical structuring component of the native invertebrate community of soft-bottom environments where this species was introduced along the coast of southern South America.