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Teck S.J.,University of California at Santa Barbara | Lorda J.,Tijuana River National Estuarine Research Reserve | Lorda J.,Autonomous University of Baja California | Shears N.T.,University of Auckland | And 6 more authors.
Biological Conservation | Year: 2017

Species targeted by fishing often recover in abundance and size within marine protected areas (MPAs) resulting in increased reproductive potential. However, in some situations, concomitant changes in the abundance of predators, competitors, or prey within MPAs, or strong gradients in the surrounding environmental seascape may counteract the purported benefits making it more difficult to predict how species will respond to protection. We used a network of MPAs in California, spanning a large temperature gradient, to investigate the drivers of demographic variability in the commercially important red sea urchin Mesocentrotus franciscanus. We investigated how demographic metrics varied geographically in response to protection, temperature, and the main sea urchin resource, the giant kelp Macrocystis pyrifera. We found significant conservation benefits to this fished sea urchin within MPAs designated six years prior to the beginning of this study. Within MPAs, red sea urchins were generally larger resulting in greater adult biomass density and reproductive biomass density. In addition, kelp density was an important explanatory variable of all red sea urchin demographic traits examined (adult size, gonadosomatic index [GSI], density, adult biomass density, and reproductive biomass density). Kelp density was positively correlated with red sea urchin GSI and adult size, but the relationships with density, adult biomass density, and reproductive biomass density were complex and the directionality changed depending on the region (or environmental setting) examined. Our results demonstrate that kelp, red sea urchin reproduction, and the effects of spatial management on demographic processes are tightly coupled with the oceanographic regime. © 2017 Elsevier Ltd


Crooks J.A.,Tijuana River National Estuarine Research Reserve | Crooks J.A.,Smithsonian Environmental Research Center | Chang A.L.,Smithsonian Environmental Research Center | Ruiz G.M.,Smithsonian Environmental Research Center
PeerJ | Year: 2016

In order to explore biotic attraction to structure, we examined how the amount and arrangement of artificial biotic stalks affected responses of a shrimp, Palaemon macrodactylus, absent other proximate factors such as predation or interspecific competition. In aquaria, we tested the effect of differing densities of both unbranched and branched stalks, where the amount of material in the branched stalk equaled four-times that of the un-branched. The results clearly showed that it was the amount of material, not how it was arranged, that elicited responses from shrimp. Also, although stalks were not purposefully designed to mimic structural elements found in nature, they did resemble biogenic structure such as hydroids, algae, or plants. In order to test shrimp attraction to a different, perhaps more unfamiliar habitat type, we examined responses to plastic "army men." These structural elements elicited similar attraction of shrimp, and, in general, shrimp response correlated well with the fractal dimension of both stalks and army men. Overall, these results indicate that attraction to physical structure, regardless of its nature, may be an important driver of high abundances often associated with complex habitats. © 2016 Crooks et al.


Crooks J.A.,Tijuana River National Estuarine Research Reserve | Crooks J.A.,Smithsonian Environmental Research Center | Chang A.L.,Smithsonian Environmental Research Center | Chang A.L.,University of California at Davis | Ruiz G.M.,Smithsonian Environmental Research Center
Biological Invasions | Year: 2010

Although individual ecosystems vary greatly in the degree to which they have been invaded by exotic species, it has remained difficult to isolate mechanisms influencing invader success. One largely anecdotal observation is that polluted or degraded areas will accumulate more invaders than less-impacted sites. However, the role of abiotic factors alone in influencing invisibility has been difficult to isolate, often because the supply of potential invaders is confounded with conditions thought to increase vulnerability to invasion. Here, we conducted a field experiment to test how the assemblages of exotic versus native marine invertebrates changed during community assembly under different exposure levels of a common pollutant, copper. The experiment was conducted by deploying fouling panels in a Randomized Block Design in San Francisco Bay. Panels were periodically removed, placed into buckets with differing copper concentrations, and returned to the field after 3 days. This design allowed propagule availability to the plates to be statistically independent of short-term copper exposure. The results demonstrate that copper caused significant differences in community structure. Average native species richness was significantly affected by copper exposure, but average exotic richness was not. The total native species pool within treatments exhibited a greater than 40% decline within increasing copper, while the exotic species pool did not change significantly. These results confirm that anthropogenic alteration of abiotic factors influences invader success, indicating that management strategies to reduce invader impacts should include both efforts to improve environmental conditions as well as reduce invader supply. © 2010 The Author(s).


McLaughlin K.,Southern California Coastal Water Research Project | Sutula M.,Southern California Coastal Water Research Project | Busse L.,San Diego Regional Water Quality Control Board | Anderson S.,California State University, Channel Islands | And 5 more authors.
Estuaries and Coasts | Year: 2014

The magnitude and extent of eutrophication was assessed at 27 segments in 23 estuaries in the Southern California Bight (SCB) between October 2008 and 2009. We applied thresholds from the existing assessment frameworks from both the European Union and the U.S. National Eutrophication Assessment to measurements of three indicators [macroalgae biomass and cover, phytoplankton biomass, and dissolved oxygen (DO) concentration] to categorize eutrophic condition in each estuary. Based on these frameworks, a large fraction of segments had moderate or worse eutrophic condition-78 % based on macroalgae, 39 % for phytoplankton, and 63 % for DO. Macroalgal biomass exceeding 70 g dw m-2 and 25 % cover was found at 52 % of sites during any sampling event and in 33 % of segments for 8 weeks or longer, a duration found to negatively impact benthic infauna. Duration of hypoxic events (DO < 4 mg L-1) was typically short, with most events less than one day; although 53 % of segments had at least one event longer than 24 h. Assessment frameworks of eutrophic condition are likely to evolve over time as the body of literature on eutrophication grows, including aspects such as the applicability of indicators in specific habitat types, indicator thresholds, and how event frequency and duration are incorporated. This paper informs this debate by discussing how eutrophic conditions in SCB estuaries are categorized using different indicators and thresholds. To this end, categorization of estuarine eutrophic condition was found to be very sensitive to the type of threshold, how data are integrated to represent duration or spatial extent, and how indicators are used as multiple lines of evidence. © 2013 Coastal and Estuarine Research Federation.


Bonel N.,National University of the South | Bonel N.,CONICET | Lorda J.,University of California at Santa Barbara | Lorda J.,Tijuana River National Estuarine Research Reserve
Malacologia | Year: 2015

The freshwater mussel Limnoperna fortunei is adapted to colonize a wide range of aquatic environments, and its ability to contend with environmental stress through phenotypic plasticity has allowed this species to successfully colonize and become established in new regions. Only limited information is currently available on the wide intraspecific variability of this species in response to environmental heterogeneity. Here, we tested the hypotheses that (1) growth and body weight of mussels from a highly polluted environment differed from those from a less polluted habitat, and (2) growth parameters estimated in this study differed from those reported for other invaded ecosystems. We conducted controlled field experiments in two study sites with differing levels of pollution. To compare our results to those reported elsewhere, we considered growth data from studies performed in different locations. We found that mussels from the more polluted habitat showed lower shell growth and body weight than those from the less polluted environment. We also observed differences in the growth performances of the golden mussel between our estimates and those from other invaded habitats. Our findings provide useful information to better understand the striking intraspecific variability of this species in response to stressful conditions. Knowledge on the phenotypic plasticity of L. fortunei is essential for predicting and managing this species.


Hopper J.V.,University of California at Berkeley | Kuris A.M.,University of California at Santa Barbara | Lorda J.,University of California at Santa Barbara | Lorda J.,Tijuana River National Estuarine Research Reserve | And 3 more authors.
Journal of Biogeography | Year: 2014

Aim: To improve our understanding of how parasitism interacts with geographical range expansions by quantifying diversity and abundance of parasites in 25 populations of a large marine snail, Kellet's whelk (Kelletia kelletii), throughout its historical and recently expanded range, which are separated by a well-known biogeographical boundary. Location: California coast (western North America). Methods: Parasitological examinations were conducted on 199 whelks from 25 subtidal reefs throughout its expanded and historical ranges. We calculated infection risk, parasite intensity, and parasite species diversity. Abiotic (temperature, latitude, distance from range limit) and biotic (host density) variables were analysed as potential drivers of differential parasitism between expanded- and historical-range populations. Results: Compared with historical-range whelks, expanded-range whelks were 20% as likely to be infected by parasites, and those that were infected had 6% the number of individual parasites. On average, expanded-range whelks had 14% the number of parasite species than the historical-range whelks. The marked decrease in species richness of parasites infecting expanded-range whelks was only partly explained by the low numbers of parasites. The reduced parasite abundance and diversity in the expanded-range whelks was not explained by the examined abiotic factors or by whelk density. Main conclusions: Expanded-range populations of Kellet's whelk experience substantially lower parasite abundance and diversity than the historical-range populations, despite relatively poor demographic performance. The reduced parasitism observed resembles the enemy escape typically characterizing invasive species. A possible explanation for the observed 'parasite escape' is that the biogeographical boundary limits the movements or drives the low abundance of other host species (elasmobranchs) required to complete the life cycles of the 'missing' parasites. We suggest that parasite escape may generally characterize range-margin expansions and be important in permitting expansions into what may otherwise be marginal habitats. This parasite escape may directly counter the spread of infectious diseases associated with global warming-induced range shifts. © 2014 John Wiley & Sons Ltd.


Uyeda K.A.,San Diego State University | Deutschman D.H.,San Diego State University | Crooks J.A.,Tijuana River National Estuarine Research Reserve
Estuaries and Coasts | Year: 2013

Native plants in the upland to high-marsh transition zone of southern California salt marshes are mostly perennials and therefore experience the abiotic stress of low soil moisture and high soil salinity throughout much of the year. However, many annual non-native plants reproduce during the brief period of reduced salinity and increased moisture during winter rainfall. We investigated the seasonal and spatial variation in vegetation and soil properties of the transition zone using an observational study. Next, we explored the potential for managing non-native plants using a field experiment with varying timing, quantity, and frequency of salt addition treatments. The observational study showed that the distribution of non-native plants is related to changes in soil salinity and soil moisture that accompany changes in elevation, although there are variations among species. In the field experiment, salt was effective at reducing non-native plant cover, but the timing of treatment was important. Although additional work is needed to refine the salt treatments, this work supports the idea that altering abiotic conditions can effectively reduce the presence of non-native species in the upland to high-marsh transition zone. © 2013 Coastal and Estuarine Research Federation.


Jones C.G.,Cary Institute of Ecosystem Studies | Jones C.G.,Agro ParisTech | Gutierrez J.L.,Grupo de Investigacion y Educacion en Temas Ambientales GrIETA | Gutierrez J.L.,University of the Sea | And 4 more authors.
Oikos | Year: 2010

While well-recognized as an important kind of ecological interaction, physical ecosystem engineering by organisms is diverse with varied consequences, presenting challenges for developing and using general understanding. There is also still some uncertainty as to what it is, and some skepticism that the diversity of engineering and its effects is amenable to conceptual integration and general understanding. What then, are the key cause/effect relationships and what underlies them? Here we develop, enrich and extend our extant understanding of physical ecosystem engineering into an integrated framework that exposes the essential cause/effect relationships, their underpinnings, and the interconnections that need to be understood to explain or predict engineering effects. The framework has four cause/effect relationships linking four components: 1. An engineer causes structural change; 2. Structural change causes abiotic change; 3. Structural and abiotic change cause biotic change; 4. Structural, abiotic and biotic change can feedback to the engineer. The first two relationships describe an ecosystem engineering process and abiotic dynamics, while the second two describe biotic consequence for other species and the engineer. The four relationships can be parameterized and linked using time-indexed equations that describe engineered system dynamics. After describing the relationships we discuss the utility of the framework; how it might be enriched; and briefly how it can be used to identify intersections of ecosystem engineering with fields outside ecology. © 2010 The Authors.


Gerard C.,CNRS Ecosystems, Biodiversity, and Evolution Laboratory | Miura O.,Kochi University | Lorda J.,University of California at Santa Barbara | Lorda J.,Tijuana River National Estuarine Research Reserve | And 3 more authors.
Hydrobiologia | Year: 2016

The globally successful invasive snail, Potamopyrgus antipodarum (Tateidae), is rarely parasitized except in its native New Zealand where it is infected as first intermediate host by at least 20 species of trematode parasitic castrators. In France and Poland, only one trematode parasitic castrator, belonging to the Aporocotylidae (the blood flukes of fishes), is known to infect P. antipodarum, and its origin remains a mystery. We investigated the genetic identities, taxonomic relationships, and prevalences of this parasite and other aporocotylids infecting P. antipodarum and closely related snails in a French stream, and throughout New Zealand and southeast Australia. ITS2 DNA sequences of the French parasite matched with Aporocotylid sp. I (sensu Hechinger, 2012) from P. antipodarum in New Zealand. Hence, the aporocotylid parasite in Europe most likely originated from the native range of the introduced host. Aporocotylid sp. I was rare in both native and invasive ranges, infecting overall less than 1 out of 1,000 snails. The parasite and its host have a persistent relationship in France, as they both were repeatedly encountered over a period of 14 years. Our molecular phylogeny also reveals that this parasite is part of a diverse and poorly known group of aporocotylids in New Zealand and southeastern Australia. © 2016 Springer International Publishing Switzerland


Lorda J.,University of California at Santa Barbara | Lorda J.,Tijuana River National Estuarine Research Reserve | Hechinger R.F.,University of California at Santa Barbara | Hechinger R.F.,University of California at San Diego | And 4 more authors.
Ecosphere | Year: 2016

The California horn snail, Cerithideopsis californica, and the shore crabs, Pachygrapsus crassipes and Hemigrapsus oregonensis, compete for epibenthic microalgae, but the crabs also eat snails. Such intraguild predation is common in nature, despite models predicting instability. Using a series of manipulations and field surveys, we examined intraguild predation from several angles, including the effects of stage-dependent predation along with direct consumptive and nonconsumptive predator effects on intraguild prey. In the laboratory, we found that crabs fed on macroalgae, snail eggs, and snails, and the size of consumed snails increased with predator crab size. In field experiments, snails grew less in the presence of crabs partially because snails behaved differently and were buried in the sediment (nonconsumptive effects). Consistent with these results, crab and snail abundances were negatively correlated in three field surveys conducted at three different spatial scales in estuaries of California, Baja California, and Baja California Sur: (1) among 61 sites spanning multiple habitat types in three estuaries, (2) among the habitats of 13 estuaries, and (3) among 34 tidal creek sites in one estuary. These results indicate that shore crabs are intraguild predators on California horn snails that affect snail populations via predation and by influencing snail behavior and performance. © 2016 Lorda et al.

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