Use of historical isoscapes to develop an estuarine nutrient baseline

Coastal eutrophication is a prevalent threat to the healthy functioning of ecosystems globally. While degraded water quality can be detected by monitoring oxygen, nutrient concentrations, and algal abundance, establishing regulatory guidelines is complicated by a lack of baseline data (e.g., pre-Anthropocene). We use historical carbon and nitrogen isoscapes over ~300 years from sediment cores to reconstruct spatial and temporal changes in nutrient dynamics for a central California estuary, Elkhorn Slough, where development and agriculture dramatically enhanced nutrient inputs over the past century. We found strong contrasts between current sediment stable isotopes and those from the recent past, demonstrating shifts exceeding those in previously studied eutrophic estuaries and substantial increases in nutrient inputs. Comparisons of contemporary with historical isoscapes also revealed that nitrogen sources shifted from a historical marine-terrestrial gradient with higher δ15N near the inlet to amplified denitrification at the head and mouth of the modern estuary driven by increased N inputs. Geospatial analysis of historical data suggests that an increase in fertilizer application – rather than population growth or increases in the extent of cultivated land – is chiefly responsible for increasing nutrient loads during the 20th century. This study demonstrates the ability of isotopic and stoichiometric maps to provide important perspectives on long-term shifts and spatial patterns of nutrients that can be used to improve management of nutrient pollution

Culturing for conservation: the need for timely investments in reef aquaculture

Temperate oyster and tropical coral reefs are analogous systems that create habitat for economically, ecologically, and culturally important species, and they provide countless ecosystem services to human coastal communities. Globally, reefs are imperiled by multiple anthropogenic stressors, particularly climate impacts. Using aquaculture to support conservation goals - known as conservation aquaculture - is a relatively new approach for many reef building species, but it shows great promise for promoting species recovery and bolstering resilience to stressors. Concerns about aquaculture-associated risks, both known and potential, have often restricted the implementation of this tool to an emergency intervention following dramatic declines on reefs, when species or systems were unlikely to recover. Here, we combine expertise from coral and oyster reef ecosystems to consider the role of aquaculture as a conservation intervention for reefs, and provide recommendations for its timely development and targeted implementation. We highlight the importance of evaluating reef systems - alongside local stakeholders and Indigenous communities - to determine where and when the benefits of using aquaculture are most likely to outweigh the risks. We spotlight the importance of proactive monitoring to detect reef population declines, and the value of early aquaculture interventions to increase efficacy. Novel aquaculture approaches and technologies specifically designed for reef builders are considered, including techniques for building complex, multi-generational and multi-species reefs. We address the need for scaling up aquaculture-assisted reef recovery, particularly of corals, using high volume methods like those that have been successfully employed for oysters. We also recommend the immediate assessment and development of techniques to increase climate resilience of reef builders and we identify the challenges and trade-offs of these approaches. We highlight the use of proof-of-concept projects to test these promising methods, and we advise tracking of all interventions over time to determine their long-term efficacy. Finally, we outline opportunities to leverage novel partnerships among conservation, industry, and community interests that utilize aquaculture to facilitate the conservation of reefs. Developing conservation aquaculture approaches now is critical to position managers, scientists, and restoration practitioners to implement this intervention in timely and effective ways to support resilient reef and human communities worldwide

Sexual Modes in the Colonial Kamptozoan Genus Barentsia

Volume: 193Start Page: 163End Page: 17

A review of the invertebrate phylum Kamptozoa (Entoprocta) and synopsis of kamptozoan diversity in Australia and New Zealand

Volume: 126Start Page: 1End Page: 2

Do a threatened native amphibian and its invasive congener differ in response to human alteration of the landscape?

Anthropogenic changes to habitat are a global phenomenon and the impact of these changes may act in tandem to cause loss of biodiversity. One major global change is the introduction of invasive species. In order to determine whether other human impacts might correlate with populations of invaders, we examined the habitat correlates of distribution, persistence and reproduction of a global invader, the American bullfrog (Rana catesbeiana). We then compared these correlates with those of a threatened, native congener, the California red-legged frog (Rana draytonii). We found striking differences between the two species in response to habitat fragmentation and degradation. Our work suggests that human alteration of habitat, in particular the hydrology of freshwater sites and through building roads, favors this invasive species across the landscape

Flight or fight: flexible antipredatory strategies in porcelain crabs

Autotomy, the voluntary shedding of limbs or other body parts in the face of predation, is a highly effective escape mechanism that has evolved independently in a variety of taxa. Crabs are unusual in that the limb that is typically sacrificed during autotomy, the anterior clawed cheliped, can also be used to ward off attack. During an encounter with a predator, an individual must thus decide between two mutually exclusive strategies: flight or fight. We used experimental predation encounters with two species of porcelain crabs (genus Petrolisthes) to examine the factors that influence the decision to flee versus fight and to determine the degree to which this decision is context-dependent. We found that autotomy was highly conditional. The characteristics that best predicted autotomy--smaller body size or female gender--also correlated with a lower escape rate by the alternative escape tactic, struggling and pinching the predator. Variation among individuals in the benefit of autotomy (relative to alternative tactics) appears to drive variation in propensity to autotomize. Porcelain crabs thus demonstrate adaptive flexibility, employing the costly strategy of autotomizing a limb as a last resort, only when their chance at success by struggling is low. Copyright 2005.autotomy; body size; decapod crustacean; flexible defense strategy; Petrolisthes; predation

Habitat differences in marine invasions of central california. Biol Invasions 7:935–48

Abstract We carried out a two-part investigation that revealed habitat differences in marine invertebrate invasions. First, we compared invasion levels of hard vs soft substrata in Elkhorn Slough, an estuary in Central California, by comparing abundance and richness of native vs exotic species in quantitative samples from each habitat type. Our results revealed that the hard substrata were much more heavily invaded than the soft substrata. Nearly all the hard substrata in Elkhorn Slough, as in most estuaries along the Pacific coast of North America, are artificial (jetties, rip-rap, docks). Some exotic species may by chance be better adapted to this novel habitat type than are natives. Two major vectors responsible for marine introductions, oyster culturing and ship-hull fouling, are also more likely to transport species associated with hard vs soft substrata. Secondly, we compared estuarine and open coast invasion rates. We examined species richness in Elkhorn Slough and adjacent rocky intertidal habitats along the Central California coast. The absolute number of exotic species in the estuary was an order of magnitude higher than along the open coast (58 vs 8 species), as was the percentage of the invertebrate fauna that was exotic (11% vs 1%). Estuaries on this coast are geologically young, heavily altered by humans, and subject to numerous transport vectors bringing invasive propagules: all these factors may explain why they are strikingly more invaded than the open coast. The finding that the more species rich habitat -the open coast -is less invaded is in contrast to many terrestrial examples, where native and exotic species richness appear to be positively correlated at a broad geographic scale