Sea Urchins Predation Facilitates Coral Invasion in a Marine Reserve

Macroalgae is the dominant trophic group on Mediterranean infralittoral rocky bottoms, whereas zooxanthellate corals are extremely rare. However, in recent years, the invasive coral Oculina patagonica appears to be increasing its abundance through unknown means. Here we examine the pattern of variation of this species at a marine reserve between 2002 and 2010 and contribute to the understanding of the mechanisms that allow its current increase. Because indirect interactions between species can play a relevant role in the establishment of species, a parallel assessment of the sea urchin Paracentrotus lividus, the main herbivorous invertebrate in this habitat and thus a key species, was conducted. O. patagonica has shown a 3-fold increase in abundance over the last 8 years and has become the most abundant invertebrate in the shallow waters of the marine reserve, matching some dominant erect macroalgae in abundance. High recruitment played an important role in this increasing coral abundance. The results from this study provide compelling evidence that the increase in sea urchin abundance may be one of the main drivers of the observed increase in coral abundance. Sea urchins overgraze macroalgae and create barren patches in the space-limited macroalgal community that subsequently facilitate coral recruitment. This study indicates that trophic interactions contributed to the success of an invasive coral in the Mediterranean because sea urchins grazing activity indirectly facilitated expansion of the coral. Current coral abundance at the marine reserve has ended the monopolization of algae in rocky infralittoral assemblages, an event that could greatly modify both the underwater seascape and the sources of primary production in the ecosystem.

Experimental evidence that intra-specific competition in seagrass meadows reduces reproductive potential in the sea urchin Paracentrotus lividus (Lamarck)

To better understand the biological controls that regulate sea urchin dynamics, we studied the effects of potential inter- and intra-specific competition for food on several biological variables of the main sea urchin in the Mediterranean (Paracentrotus lividus). We carried out a caging experiment in which we manipulated sea urchin density (natural vs. high density) and herbivorous fish (Sarpa salpa) accessibility (free access vs. exclusion) in a Posidonia oceanica meadow. No evidence of competition between fish and urchins was detected. Neither density-dependent mortality nor changes in the somatic variables were found; however, we detected that intra-specific competition affected the reproductive potential of P. lividus. The gonad index of urchins at high population densities was ca. 30% lower than that of urchins at natural densities. As a spawning event had just occurred when urchins were collected, these differences probably reflect differences in reserve content, which may compromise the following reproductive period and decrease survival in the long term, as the gonads are also used as storage organs. For the time period studied, mortality rates appeared to be independent of local densities. The results indicate that a long-term negative feedback mechanism appears to take place in P. lividus in response to increased population density.

Avaluació de la població de corall Corallium rubrum de les Illes Medes. Any 1995

Podeu consultar l'Informe complet a: http://hdl.handle.net/2445/24663

Avaluació de la població de corall Corallium rubrum de les Illes Medes. Exercici 1999

Podeu consultar l'Informe complet a: http://hdl.handle.net/2445/23667

Avaluació de l'impacte de l'expoli de corall vermell (Corallium rubrum) de la zona protegida de les Illes Medes detectat durant l'hivern de 2000

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Avaluació de la població de corall Corallium Rubrum de les Illes Medes. Exercici 2000

Podeu consultar l'Informe complet a: http://hdl.handle.net/2445/23669

Avaluació de la població de corall Corallium Rubrum de les Illes Medes. Exercici 2001

Podeu consultar l'Informe complet a: http://hdl.handle.net/2445/23672

Effects of season, sex and body size on the feeding ecology of turtle-headed seasnakes (Emydocephalus annulatus) on IndoPacific inshore coral reefs

In terrestrial snakes, many cases of intraspecific shifts in dietary habits as a function of predator sex and body size are driven by gape-limitation - and hence, are most common in species that feed on relatively large prey, and exhibit a wide body-size range. Our data on seasnakes reveal an alternative mechanism for intraspecific niche partitioning, based on sex-specific seasonal anorexia induced by reproductive activities. Turtle-headed seasnakes (Emydocephalus annulatus) on coral reefs in the New Caledonian Lagoon feed entirely on the eggs of demersal-spawning fishes. DNA sequence data (cytochrome b gene) on eggs that we palpated from stomachs of 37 snakes showed that despite this ontogenetic-stage specialization, the prey come from a taxonomically diverse array of species including damselfish (41% of samples, at least 5 species), blennies (41%, 4 species) and gobies (19%, 5 species). The composition of snake diets shifted seasonally (with damselfish dominating in winter but not summer), presumably reflecting seasonality of fish reproduction. That seasonal shift affects male and female snakes differently, because reproduction is incompatible with foraging. Adult female seasnakes ceased feeding when they became heavily distended with developing embryos in late summer, and males ceased feeding while they were mate-searching in winter. The sex divergence in foraging habits may be amplified by sexual size dimorphism; females grow larger than males, and larger snakes (of both sexes) feed more on damselfish (which often lay their eggs in exposed sites) than on blennies and gobies (whose eggs are hidden within narrow crevices). Specific features of reproductive biology of coral-reef fish (seasonality and nest type) have generated intraspecific niche partitioning in these seasnakes, by mechanisms different from those that apply to terrestrial snakes.

Avaluació de la població de corall Corallium Rubrum de les Illes Medes. Exercici 2002

Podeu consultar l'Informe complet a: http://hdl.handle.net/2445/23675

Avaluació de la població de Corall (Corallium rubrum) de les Illes Medes. Exercici 2003

Podeu consultar l'Informe complet a: http://hdl.handle.net/2445/23677

Predicting the mating system from phenotypic correlations between life-history and sperm quality traits in the Alpine whitefish Coregonus zugensis

The mating behavior and reproductive strategies of Alpine whitefish like Coregonus zugensis (Nusslin) are poorly understood, probably because they spawn in deep water where direct observations are difficult. In this study, we interpret life-history and sperm quality traits of fish that we caught from their spawning place. We found that males invest heavily into gonadal tissue (up to 5.6% of their body weight), which is, in comparison to other fish, consistent with external fertilization, distinct pairing and moderate to high communal spawning, or no pairing and low to moderate communal spawning. Sperm competition theory and recent experimental studies on other salmonids predict that males optimize ejaculate characteristics in relation to the costs of sperm and the level of competition they have to expect: dominant males are predicted to invest less into ejaculate quality and to have slower spermatozoa than subdominant males. We found that spermatozoa of older males are slower than those of younger males. Moreover, older males have larger breeding tubercles, a secondary sexual trait that has, in some previous studies, been found to be linked to good condition and to good genetic quality. Our results suggest that C. zugensis has age-linked reproductive strategies, that multimale spawning is common, i.e., that sperm competition plays a significant role, and that older males are on average dominant over younger males at the spawning place.

Persistent unequal sex ratio in a population of grayling (salmonidae) and possible role of temperature increase.

In some fishes, water chemistry or temperature affects sex determination or creates sex-specific selection pressures. The resulting population sex ratios are hard to predict from laboratory studies if the environmental triggers interact with other factors, whereas in field studies, singular observations of unusual sex ratios may be particularly prone to selective reporting. Long-term monitoring largely avoids these problems. We studied a population of grayling (Thymallus thymallus) in Lake Thun, Switzerland, that has been monitored since 1948. Samples of spawning fish have been caught about 3 times/week around spawning season, and water temperature at the spawning site has been continuously recorded since 1970. We used scale samples collected in different years to determine the average age of spawners (for life-stage specific analyses) and to identify the cohort born in 2003 (an extraordinarily warm year). Recent tissue samples were genotyped on microsatellite markers to test for genetic bottlenecks in the past and to estimate the genetically effective population size (N(e) ). Operational sex ratios changed from approximately 65% males before 1993 to approximately 85% males from 1993 to 2011. Sex ratios correlated with the water temperatures the fish experienced in their first year of life. Sex ratios were best explained by the average temperature juvenile fish experienced during their first summer. Grayling abundance is declining, but we found no evidence of a strong genetic bottleneck that would explain the apparent lack of evolutionary response to the unequal sex ratio. Results of other studies show no evidence of endocrine disruptors in the study area. Our findings suggest temperature affects population sex ratio and thereby contributes to population decline. Persistencia de Proporción de Sexos Desigual en una Población de Tímalos (Salmonidae) y el Posible Papel del Incremento de la Temperatura.

08009-005 Storm Lake Watershed Final Report

Storm Lake, the state's fourth largest natural lake, has been the centerpiece of significant economic development, including a resort, water park, and state marina. While there have been considerable improvements to the lake's water quality through a major on-going lake restoration program and watershed project, the Little Storm Lake area still needs to be addressed. Little Storm Lake is a 190 acre area on the nmihwest side of Storm Lake. The water level in both areas is based on the dam height located on the southeast corner of Storm Lake. Approximately 70% of the water from the watershed flows through Little Storm Lake. Little Storm Lake originally had the ability to remove much of the sediment and nutrients from incoming waters. However, due to degradation, proper wetland function has been compromised. Under normal hydrologic conditions Little Storm Lake has the potential to function as a sediment trap for Storm Lake, but tllis capacity is overwhelmed during high flows. Little Storm Lake is at or near its sediment trapping capacity, which results in higher sediment transport into Storm Lake. Resuspension of sediments due to wind and other in-lake dynamics, such as rough fish, further exacerbate the total turbidity from suspended sediment and results in movement of sediment from Little Storm Lake into Storm Lake. This project includes a fish barrier and water retention structure between Little Storm Lake and Storm Lake and the construction of a pumping station and associated equipment. The project involves periodic dewatering of Little Storm Lake during years of favorable climatological conditions to consolidate the sediments and revegetate the area. Construction of the fish banier would aid restoration efforts by preventing rough fish from destroying the vegetation and would decrease recruitment of rough fish by limiting their spawning area. In the future, if the diminished trapping capacity of Little Storm Lake still results in sediment moving into Storm Lake, a dredging project would be initiated to deepen Little Storm Lake.

07021-008 Sand Creek Watershed Final Report

Sand Creek is the most significant recreational fishery in Delaware County because of its location to Manchester and Lake Delhi. It is a feeder stream for game fish to the main stem of the Maquoketa River which is limited by the dams at Manchester and Lake Delhi. Sand Creek encompasses 16,045 acres and is dominated by row crop agriculture. It is being impacted by sediment, nutrients and E coli bacteria. Sand Creek will be a good example for habitat impaired watershed. The purpose of this project is to decrease the amount of sediment and nutrients reaching Sand Creek and to increase the habitat in Sand Creek to make it a better spawning and growing area for the fish and the food chain for the fish. The objectives of this project are to reduce sediment delivery by 40%, to improve in-stream habitat on 40% of identified critical areas and implement an information/education program. The project will install 3,800 acres of new no-till planting, 6 water and sediment control basins, 4,000 feet of terraces, 20,000 feet of improved or new waterways, 3,200 feet of streambank/ habitat enhancement, 4,500 feet of livestock exclusion fencing and 6 acres of wetlands.

1009-004 Lost Island Lake Watershed Final Report

The Lost Island Lake watershed is located in the prairie pothole region, a region dotted with glacial wetlands and shallow lakes. At 1,180 acres, Lost Island Lake is the state's fifth largest natural lake and its watershed is comprised of nearly 1,000 acres of wetland habitat, including Iowa 's largest natural wetland – Barringer Slough. Unfortunately, Lost Island and its associated wetlands are not functioning to their fullest ecological and water quality potential. In 2002 and 2004, Lost Island Lake was categorized as '·impaired'" on Iowa's Impaired Waters List. Frequent algal blooms and suspended solids drastically increase turbidity levels resulting in its impairment. To investigate these concerns, a two-year study and resulting Water Quality Improvement Plan were completed. The water quality study identified an overabundance of non-native common carp (Cyprinus carpio) in the lake and its surrounding wetlands as a primary cause of impairment. The goal of the Lost Island Lake Watershed Enhancement Project is to restore ecological health to Lost Island Lake and its intricate watershed resulting in improved water quality and a diverse native plant and wildlife community. The purpose of this grant is to obtain funding for the construction of two combination fish barriers and water control structures placed at key locations in the watershed within the Blue Wing Marsh complex. Construction of the fish barriers and water control structures would aid restoration efforts by preventing spawning common carp from entering wetlands in the watershed and establishing the ability to manage water levels in large wetland areas. Water level management is crucial in wetland health and exotic fish control. These two structures are part of a larger construction project that involves a total of four combination fish barriers and water control structures and one additional fish barrier. The entire Lost Island Lake Watershed Enhancement Project is a multi-year project, but the construction phase for the fish barriers and water control structures will be completed before December 31, 2011.