Settlement, recruitment and potential predators and competitors of juvenile echinoderms in the rocky subtidal zone

Recruitment patterns of marine invertebrates are affected both by settlement and early post-settlement events. This study examined the settlement and recruitment patterns of echinoderms at three sites in the rocky subtidal zone of Bocabec Cove, Bay of Fundy, Canada using artificial turf collectors and quadrats on the natural substrate. Potential predators were quantified at two of the sites along transects and in 1-m² quadrats. Both potential predators and competitors were quantified in 0.0625-m² quadrats. Settlement varied across sites (1.5–3 km apart) and two years of sampling (2004, 2005). The site of most potential settlement differed for the three groups of echinoderms: sea urchins (Strongylocentrotus droebachiensis), sea stars (Asterias spp.) and sea cucumber (Psolus fabricii). Settlement densities on the artificial turf collectors tended to be greater than the densities of settlers on the natural substrate. On the natural substrate, the only significant difference between densities of juveniles over time was that newly settled sea stars were found in July and were not found the following October. Large lobsters and carnivorous worms were potential predators with densities that varied between sites. Potential competitors that differed in abundance between sites were herbivorous gastropods and conspecifics for sea urchins; and carnivorous worms for sea stars. This study suggests that patterns of recruitment are either set up by patterns of settlement or by events during the first few weeks/months on the benthic substrate for these echinoderms.     

COMPUTATION OF UNSTEADY FLOWS IN THE ALABAMA RIVER1

ABSTRACT: An application is described of the branch-network flow model, BRANCH, to the upper Alabama River system in central Alabama. The model is used to simulate one-dimensional unsteady flows and water surface elevations in approximately 60 river miles of the Alabama River system. Preliminary calibration was made using 72 hours of observed data. Simulated discharges are about 10 percent lower than observed discharges at higher discharge rates and computed flows lag observed flows by about 30 minutes.     

Mating behaviour of Macrophthalmus hirtipes (Brachyura: Ocypodidae)

 We examined the mating behaviour of the New Zealand ocypodid crab Macrophthalmus hirtipes in the laboratory between February and June 1998. This species has a discrete breeding season. Mating and moulting were not linked and only intermoult females with mobile gonopore opercula were attractive to males. Allometry and compatibility of gonopods and gonopores of different-sized crabs was investigated. Under laboratory conditions, the opercula of intermoult females remained mobile on average for 11.4 d, but the duration of receptivity did not appear to be under female control. The operational sex ratio in the laboratory fluctuated greatly, but was always male-dominated. During the period of opercular mobility, females mated many times with several different males. Matings in the absence of burrows were relatively short (mean duration = 23 min, max. = 122 min) and the mating behaviour of M. hirtipes lacked courtship and mate-guarding. Males used a search-intercept method to acquire mates, with very low levels of intrasexual competition. There was no evidence of mate preference in M. hirtipes, and males spent just as long mating with ovigerous females as with non-ovigerous ones. Although M. hirtipes has ventral-type spermathecae, as do several other ocypodid crabs, it is unclear whether this promotes last-male sperm precedence. The role of burrows in modifying the mating behaviour of M. hirtipes in the field remains to be established. Received: 7 January 2000 / Accepted: 5 June 2000     

Studies on the uptake of cadmium by the crab Carcinus maenas in the laboratory. I. Accumulation from seawater and a food source

The crab Carcinus maenas (L.) was exposed to radioactively labelled cadmium dissolved in seawater at concentrations of 0.1, 1 and 10 ppm, the latter concentration being toxic to the crabs (50% mortality after 12.3 days). Net accumulation of cadmium from solution was proportional to the level and time period of cadmium exposure. Total absorbed cadmium levels reached 0.0043 and 0.0412 mg Cd g^-1 dry weight after 40 days exposure to 0.1 and 1 ppm Cd, respectively, and 0.1115 mg Cd g^-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The highest tissue concentration was found in the midgut gland, reaching 0.786 mg Cd g^-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The midgut gland only contained about 10% of the total cadmium absorbed from solution, while the exoskeleton contained the bulk of obsorbed cadmium (59 to 80%) probably passively adsorbed onto the surface. When cadmium was absorbed by the crabs from a food source, the midgut gland contained 16.9% of the total absorbed cadmium whereas the exoskeleton now contained only 22.2%. Ten percent of the cadmium available in the food source (Artemia salina) was accumulated by the crabs. When placed in cadmium-free seawater, crabs that had accumulated cadmium from solution lost 69% of the absorbed cadmium in 10 days, mostly from the exoskeleton which lost 78% of its original absorbed cadmium concentration.     

不同碳源条件下草菇内切型纤维素酶基因（eg1）转录表达的分析

利用Northernblot方法分析了不同碳源条件下草菇切型纤维素酶基因(eg1)的表达.结果发现,在含有纤维素的液体培养基中生长10d,eg1在草菇菌丝中有高效表达;纤维二糖、α-乳糖、β-乳糖,也能诱导eg1的表达,但和纤维素相比,eg1的表达量相对较低,并且它们的诱导效应在加入这类糖12h后迅速减弱;槐糖和龙胆二糖的诱导作用非常弱.在天然稻草为基质的固体栽培料生长时,草菇eg1的表达和草菇菌丝生长与出菇相对应,在菌丝生长期(d8)可见eg1的表达,d12时菌丝已长满,表达减弱,在出菇及菇体的分化及增大期,eg1的表达量逐渐增强,在成熟期达到最高水平;表明在草菇菇体发育中需要更多碳源及能源的补充,eg1在这方面起着非常重要的作用.图4参14     

COMPARING SAMPLING SCHEMES FOR MONITORING POLLUTANT EXPORT FROM A DAIRY PASTURE1

ABSTRACT: Dairy cow pastures and feeding areas around barns can be a significant source of nonpoint source pollutants to nearby streams. To help document the significance of these sources, nutrient export in streamfiow from a 56.7-ha, mostly agricultural, watershed located in southwestern North Carolina was monitored from August 1994 to January 1996. Total nitrogen and phosphorus export rates from the upper, predominantly pasture, part of the watershed were 18.0 and 1.4 kg/ha/yr, respectively, as measured by weekly grab sampling and 18.7 and 4.9 kg/halyr, respectively, as measured from storm event monitoring. Nitrogen and phosphorus export rates for the area between the monitoring sites, which included overgrazed cow holding and feeding areas and farm buildings, were 376 and 86 kgfhalyr, respectively, for grab sampling and 351 and 160 kg/ha/yr, respectively, for storm event monitoring. To estimate the amount of reduction from nonpoint source controls necessary to effect a significant reduction in pollutant loading, statistical analyses of the load data were conducted. The analyses for the five pollutants monitored showed that total suspended solids would require the greatest reduction (34.6 percent for weekly grab and 33.6 percent for storm) in loading after the implementation of controls for statistical significance. Nitrate plus nitrite was found to require the least reduction (12.6 percent for weekly grab). Pollutant export rates computed from weekly grab samples and storm event samples used separately were compared to corresponding export rates computed from combining grab and storm event samples to assess the differences in monitoring schemes.     

Assessment of the aquatic biodiversity of a threatened coastal lagoon at Bimini, Bahamas

Coastal biodiversity is threatened worldwide by both direct and indirect anthropogenic activities. To more effectively manage and protect coastal biodiversity, accurate assessments of genetic, species, and ecosystem level diversity are required. We present the results from an assessment of the aquatic species diversity of a small (3?km²), shallow, mangrove-fringed Bahamian lagoon (the North Sound) subject to ongoing anthropogenic development. The assessment was conducted through a collation of field observations and data in published literature. We found that eight angiosperm species, 30 macroalgal species, and 370 animal species (including 95 fishes, 69 arthropods, 56 birds, and 45 mollusks) were documented within the lagoon. At least 11 of these species are of conservation concern, such as the critically endangered smalltooth sawfish (Pristis pectinata) and hawksbill turtle (Eretmochelys imbricata). Comparisons of community similarity indicated that the North Sound has a relatively distinct fauna and flora, but available data suggest that the species found there are most similar to those found in nearby habitats in Cuba. The lagoon forms a key nursery habitat for many species, including lemon sharks (Negaprion brevirostris), Caribbean spiny lobsters (Panulirus argus), and queen conch (Strombas gigas). Recently, the lagoon was included as part of a new marine protected area (MPA), but much of the habitat has already experienced considerable anthropogenic disturbance and the MPA boundaries have yet to be established. We have therefore analyzed the lagoon biodiversity and expect the data presented here to serve as a baseline for future comparisons.     

Tasmanian landowner preferences for conservation incentive programs: a latent class approach

An empirical model of landowners' conservation incentive program choice is developed in which information about landowners' socio-economic and property characteristics and their attitudes, is combined with incentive program attributes. In a Choice survey landowners were presented with the choice of two incentive programs modelled as 'bundles of attributes' mimicking a voluntary choice scenario. Landowner behaviour and decision and the type of conditions and regulations they preferred were analyzed. Based on choice survey data, landowner heterogeneity was accounted for using a latent class approach to estimate the preference parameters. Three latent classes of landowners with different attitudes to the role and outcome of establishing conservation reserves on private land were identified: multi-objective owners; environment owners; and production owners. Only a small proportion of landowners, mostly environment owners, would voluntarily join a program. Although compensation funding contributed to voluntary program choice for multi-objective owners and environment owners, welfare losses were around 4000 AUD per hectare, which is less than the average agricultural land value in Tasmania. Landowners for whom compensation funding contributed to voluntary program choice were also most likely to set aside land for conservation without payment. This raises the possibility that the government's compensation expenditure could potentially be either reduced or re-allocated to landowners who will not voluntarily take conservation action. Increasing participation in conservation incentive programs and minimizing the welfare losses associated with meeting conservation targets may be best achieved by offering programs that allow flexibility in terms of legal arrangements and other program attributes.     

A landscape-scale framework to identify refugia from multiple stressors

From a conservation perspective, quantifying potential refugial capacity has been predominantly focused on climate refugia, which is critical for maintaining the persistence of species and ecosystems. However, protection from other stressors, such as human-induced changes in fire and hydrology, that cause habitat loss, degradation, and fragmentation is also necessary to ensure that conservation efforts focused on climate are not undermined by other threats. Thus, conceptual and methodological advances for quantifying potential refugia from multiple anthropogenic stressors are important to support conservation efforts. We devised a new conceptual approach, the domains of refugia, for assessing refugial capacity that identifies areas where exposure to multiple stressors is low. In our framework, patterns of environmental variability (e.g., increased frequency of warm summers), thresholds of resilience, and extent and intensity of stressors are used to identify areas of potential refugia from a suite of ongoing anthropogenic stressors (e.g., changes in fire regime). To demonstrate its utility, we applied the framework to a Southern California landscape. Sites with high refugial capacity (super-refugia sites) had on average 30% fewer extremely warm summers, 20% fewer fire events, 10% less exposure to altered river channels and riparian areas, and 50% fewer recreational trails than the surrounding landscape. Our results suggest that super-refugia sites (∼8200 km²) for some natural communities are underrepresented in the existing protected area network, a finding that can inform efforts to expand protected areas. Our case study highlights how considering exposure to multiple stressors can inform planning and practice to conserve biodiversity in a changing world.