Marine reserves reestablish lost predatory interactions and cause community changes in rocky reefs.

In the last decades, marine reserves have dramatically increased in number worldwide. Here I examined the potential of no-take marine reserves to reestablish lost predatory interactions and, in turn, cause community-wide changes in Mediterranean rocky reefs. Protected locations supported higher density and size of the most effective fish preying on sea urchins (the sea breams Diplodus sargus and D. vulgaris) than unprotected locations. Density of sea urchins (Paracentrotus lividus and Arbacia lixula) was lower at protected than at unprotected locations. Size structure of P. lividus was bimodal (a symptom of predation on medium-sized urchins) only at the protected locations. Coralline barrens were less extended at protected than at unprotected locations, whereas turf-forming and erect-branched algae showed an opposite pattern. Erect-unbranched and erect-calcified algae and conspicuous zoobenthic organisms did not show any pattern related to protection. Tethering experiments showed that predation impact on urchins was (1) higher at protected than at unprotected locations, (2) higher on P. lividus than on A. lixula, and (3) higher on medium-sized (2-3.5 cm test diameter) than large-sized (>3.5 cm) urchins. Sea urchins preyed on by fish in natural conditions were smaller at unprotected than at protected locations. The analysis of sea urchin remains found in Diplodus fish stomachs revealed that medium-sized P. lividus were the most frequently preyed upon urchins and that size range of consumed sea urchins expanded with increasing size of Diplodus fish. These results suggest that (1) depletion and size reduction of predatory fish caused by fishing alter patterns of predation on sea urchins, and that (2) fishing bans (e.g., within no-take marine reserves) may reestablish lost interactions among strongly interactive species in temperate rocky reefs with potential community-wide effects.     

The role of life histories and trophic interactions in population recovery

Factors affecting population recovery from depletion are at the focus of wildlife management. Particularly, it has been debated how life‐history characteristics might affect population recovery ability and productivity. Many exploited fish stocks have shown temporal changes towards earlier maturation and reduced adult body size, potentially owing to evolutionary responses to fishing. Whereas such life‐history changes have been widely documented, their potential role on stock's ability to recover from exploitation often remains ignored by traditional fisheries management. We used a marine ecosystem model parameterized for Southeastern Australian ecosystem to explore how changes towards “faster” life histories might affect population per capita growth rate r. We show that for most species changes towards earlier maturation during fishing have a negative effect (3–40% decrease) on r during the recovery phase. Faster juvenile growth and earlier maturation were beneficial early in life, but smaller adult body sizes reduced the lifetime reproductive output and increased adult natural mortality. However, both at intra‐ and inter‐specific level natural mortality and trophic position of the species were as important in determining r as species longevity and age of maturation, suggesting that r cannot be predicted from life‐history traits alone. Our study highlights that factors affecting population recovery ability and productivity should be explored in a multi‐species context, where both age‐specific fecundity and survival schedules are addressed simultaneously. It also suggests that contemporary life‐history changes in harvested species are unlikely to increase their resilience and recovery ability.     

Food web structure and trophic interactions of the tropical highland lake Hayq, Ethiopia

We generated a mass-balance model to figure out the food web structure and trophic interactions of the major functional groups of the Ethiopian highland Lake Hayq. Moreover, the study lay down a baseline data for future ecosystem-based investigations and management activities. Extensive data collection has been taken place between October 2007 and May 2009. Ecotrophic efficiency (EE) of several functional groups including phytoplankton (0.8) and detritus (0.85) was high indicating the utilization of the groups within the system. However, the EE of Mesocyclops (0.03) and Thermocyclops (0.30) was very low implying these resources were rather a ‘sink’ in the trophic hierarchy. Flows based on aggregated trophic level sensu Lindeman revealed the importance of both phytoplankton and detritus to higher trophic levels. The computed average transfer efficiency of 11.5% for the first four trophic levels was within the range for highly efficient African lakes. The primary production to respiration (P/R) ratio (1.05) of Lake Hayq indicates the maturity of the ecosystem. We also modeled the food-web by excluding Tilapia and reduced phytoplankton biomass to get insight into the mass balance before Tilapia was introduced. The analysis resulted in a lower system omnivory index (SOI = 0.016) and a reduced P/R ratio (0.13) that described the lake as immature ecosystem, suggesting the introduction of Tilapia might have contributed to the maturity of the lake. Tilapia in Lake Hayq filled an ecological empty niche of pelagic planktivores, and contributed for the better transfer efficiency observed from primary production to fish yield.     

Marine reserves,fisheries ban,and 20 years of positive change in a coral reef ecosystem

By 2004, Belize was exhibiting classic fishing down of the food web. Groupers (Serranidae) and snappers (Lutjanidae) were scarce and fisheries turned to parrotfishes (Scarinae), leading to a 41% decline in their biomass. Several policies were enacted in 2009–2010, including a moratorium on fishing parrotfish and a new marine park with no-take areas. Using a 20-year time series on reef fish and benthos, we evaluated the impact of these policies approximately 10 years after their implementation. Establishment of the Southwater Caye Marine Reserve led to a recovery of snapper at 2 out of 3 sites, but there was no evidence of recovery outside the reserve. Snapper populations in an older reserve continued to increase, implying that at least 9 years is required for their recovery. Despite concerns over the feasibility of banning parrotfish harvest once it has become a dominant fin fishery, parrotfishes returned and exceeded biomass levels prior to the fishery. The majority of these changes involved an increase in parrotfish density; species composition and adult body size generally exhibited little change. Recovery occurred equally well in reserves and areas open to other forms of fishing, implying strong compliance. Temporal trends in parrotfish grazing intensity were strongly negatively associated with the cover of macroalgae, which by 2018 had fallen to the lowest levels observed since measurements began in 1998. Coral populations remained resilient and continued to exhibit periods of net recovery after disturbance. We found that a moratorium on parrotfish harvesting is feasible and appears to help constrain macroalgae, which can otherwise impede coral resilience.     

Impact of conservation areas on trophic interactions between apex predators and herbivores on coral reefs

Apex predators are declining at alarming rates due to exploitation by humans, but we have yet to fully discern the impacts of apex predator loss on ecosystem function. In a management context, it is critically important to clarify the role apex predators play in structuring populations of lower trophic levels. Thus, we examined the top‐down influence of reef sharks (an apex predator on coral reefs) and mesopredators on large‐bodied herbivores. We measured the abundance, size structure, and biomass of apex predators, mesopredators, and herbivores across fished, no‐take, and no‐entry management zones in the Great Barrier Reef Marine Park, Australia. Shark abundance and mesopredator size and biomass were higher in no‐entry zones than in fished and no‐take zones, which indicates the viability of strictly enforced human exclusion areas as tools for the conservation of predator communities. Changes in predator populations due to protection in no‐entry zones did not have a discernible influence on the density, size, or biomass of different functional groups of herbivorous fishes. The lack of a relationship between predators and herbivores suggests that top‐down forces may not play a strong role in regulating large‐bodied herbivorous coral reef fish populations. Given this inconsistency with traditional ecological theories of trophic cascades, trophic structures on coral reefs may need to be reassessed to enable the establishment of appropriate and effective management regimes. El Impacto de las Áreas de Conservación sobre las Interacciones Tróficas entre los Depredadores Dominantes y los Herbívoros en los Arrecifes de Coral     

Spatial-econometric analysis of attraction and repulsion of private conservation by public reserves

It is difficult for public agencies to make optimal reserve-site selections without knowing how new public reserves might influence the configuration of private conservation. Private land trusts protect much land in the USA, but little is known about how private groups respond to conservation decisions made by other conservation agents. To fill that gap, we analyze township-level spatial data on conservation in California, Illinois, and Massachusetts to explore relationships between the location of private and public conservation land. Using linear spatial-econometric models and Bayesian spatial probit models, we find evidence that private-protected acres are clustered together in space. In California, it appears that private land conservation is attracted towards places where the government has reserves. In Illinois and Massachusetts, however, it appears that private conservation shifts away from townships with government reserves due to a mixture of spatial repulsion and simple acreage displacement.     

Ontogenetic habitat shift and risk of cannibalism in the common chameleon (Chamaeleo chamaeleon)

Ontogenetic habitat shifts have been documented in numerous fish and amphibians and in some reptiles. Intraspecific competition together with differential predation, prey size, social interactions, size-related thermal requirements, and morphological constraints on movement are often implicated in this ontogenetic habitat separation. In the current study, we combined field observation with experiments in seminatural arenas to test various hypotheses regarding the ontogenetic habitat shift that we have documented in the common chameleon. Juveniles (mean, 1 g) occupied low grasses and the adults (mean, 35 g) were found on bushes and trees. Overlap in habitat use between these two age classes was minimal. Our field experiments showed that juveniles actively avoid the presence of adults by concealment or flight. Adults readily attacked and consumed juveniles, regardless of their own mass. These results suggest that the risk of cannibalism towards juveniles is an important selective force behind the ontogenetic habitat shift observed in the common chameleon and may be important in other species too.     

Combining DNA and morphological analyses of faecal samples improves insight into trophic interactions: a case study using a generalist predator

The diet of pinnipeds is most commonly inferred from morphologically diagnostic remains of prey in their scats. Although this method can generate quantitative estimates of diet simply, important prey types may not always be detected. DNA-based methods improve detection of prey in scats, but they are not quantitative. While some studies have combined morphological and DNA-based methods, these have only assessed prey that are represented by their hard remains in scats. To overcome this bias, we apply molecular and morphological analyses to the soft and hard portions of faecal samples respectively, to estimate the diet of lactating Antarctic fur seals (Arctocephalus gazella) on Heard Island. The diet of this population is of particular interest because it is expanding rapidly and may rely to some extent on mackerel icefish (Champsocephalus gunnari), which are subject to commercial fisheries. Based on results from morphological analysis and likely important prey types, we tested for DNA remains of C. gunnari, myctophids and squid in faecal samples. The proportion of samples (n = 54) yielding no dietary information was reduced from around 25.9% using either method alone, to 9.3% when combined. Detection of all prey types tested for was notably improved by integrating molecular and morphological data. Data from either method alone would have underestimated the number of animals consuming C. gunnari by around 25.7%. Detection of multiple prey types in samples increased from 9.3% when using morphological analysis only, to 33.3% when using DNA only, to 46.3% when using both methods. Taken in isolation, morphological data inferred that individual seals consume either C. gunnari or myctophids, probably foraging in separate locations characteristic of those prey. Including molecular data demonstrated that while this may be true of some individuals, many other seals consume a mixed diet of at least C. gunnari, myctophids and squid. This new approach of combining DNA-based and morphological analyses of diet samples markedly increased the number of samples yielding dietary information, as well as increasing the amount of information attained from those samples. Our findings illustrate the broad potential of this technique to improve insight into trophic interactions in marine ecosystems.

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Colonization and Selection of Fly-Ash Substrates by Marine Invertebrates

Fly-ash dumped on the sea bed causes a local impoverishment of the benthos. Experiments on ash in sea water have shown bacterial colonization to occur, at a slower rate than on natural silt, limited meiofaunal colonization after 18 months, selection by meroplanktonic larvae for the ash, though inhibition of development after settlement, and selection against ash by mobile benthic adults. the major inhibition to colonization is the lack of organic content in the ash.     

Colonization and Selection of Fly-Ash Substrates by Marine Invertebrates

Abstract

Fly-ash dumped on the sea bed causes a local impoverishment of the benthos. Experiments on ash in sea water have shown bacterial colonization to occur, at a slower rate than on natural silt, limited meiofaunal colonization after 18 months, selection by meroplanktonic larvae for the ash, though inhibition of development after settlement, and selection against ash by mobile benthic adults. the major inhibition to colonization is the lack of organic content in the ash.     

Spatial and mass balanced trophic models of La Rinconada Marine Reserve (SE Pacific coast), a protected benthic ecosystem: Management strategy assessment

Steady-state, dynamic, and spatial models were constructed for the benthic system of La Rinconada Marine Reserve off northern Chile (SE Pacific coast). We examined data on biomass, P/B ratios, catches, food spectrum, consumption, and the dynamics of commercial and non-commercial populations using three theoretical frameworks: Ecopath, Ecosim, and Ecospace. The biomass of the scallop Argopecten purpuratus and the clam Tagelus dombeii were the most relevant compartments of the studied ecosystem. Among the carnivores, the functional crab group Cancer spp. was the most relevant. The Rhodophyta was the dominant macroalga compartment of the system. The results obtained using mixed trophic impacts (MTI) showed that the predatory snail Thais chocolata propagated higher magnitudes of direct and indirect effects on the other species or functional groups. The sea star Luidia magallanica and Rhodophyta had the least effects on the remaining compartments. According to the Ecosim estimates (increasing mortality by fishing), the scallop A. purpuratus had the highest impact on the other compartments. The Ecospace model showed similar qualitative and quantitative effects for changes in biomass under three different exploitation scenarios (by subsystems and globally). Nevertheless, the greatest changes were provoked by using the top-down control and the vulnerabilities estimated by Ecosim. System recovery times were highest with increased mortality of the asteroid L. magallanica and the carnivorous snail T. chocolata, suggesting that the sea star could be considered to be a top predator with a top-down control. The F_MSY estimated for the scallop A. purpuratus was close to the F_i originally entered in Ecopath, limiting the design and execution of an exploitation plan within ecologically sustainable boundaries. The situation was different (F_MSY ? F_i) for the other commercial species, making possible multi-species exploitation programs. The Ecospace trophic-spatially explicit model shows a similar pattern of direct and indirect effects generated when exerting exploitation separately by subsystems. Therefore, habitat rotation of fisheries is not justified.     

Integrative trophic network assessments of a lentic ecosystem by key ecological approaches of water chemistry, trophic guilds, and ecosystem health assessments along with an ECOPATH model

The objective of this study was to describe the trophic structure and energy flow in a lentic ecosystem in South Korea. Physicochemical water conditions were evaluated along with the reservoir ecosystem health using a multimetric IBI model. Nutrient analyses of the reservoir showed a nutrient rich and hypereutrophic system. Guild analysis revealed that tolerant and omnivorous species dominated the ecosystem. Tolerant fish, as a proportion of the number of individuals, were associated (R² > 0.90, p < 0.01) with TN and TP, the key indicators of trophic state in lentic ecosystems. The mean Reservoir Ecosystem Health Assessment (REHA) score was 19.3 during the study, which was judged as in ‘fair to poor’ condition. A trophic analysis of the reservoir estimated by the ECOPATH model shows that most activity in terms of energy flow occurred in the lower part of the trophic web, where there was intensive use of primary producers as a food source. Consequently, of the 10 consumer groups, nine fell within trophic levels <2.8. Trophic levels (TL) estimated from the weighted average of prey trophic levels varied from 1.0 for phytoplankton, macrophytes, and detritus to 3.25 for the top predator, Pseudobagrus fulvidraco. Our integrated approach to trophic network analysis may provide a key tool for determining the effects of nutrient influx on energy flow pathways in lentic ecosystems.     

Stimulation of phytoplankton production in coastal waters by natural rainfall inputs: Nutritional and trophic implications

Recent evaluations of estuarine and coastal nutrient budgets implicate atmospheric deposition as a potentially significant (20 to 30%) source of biologically available nitrogen. We examined the potential growth stimulating impact of atmospheric nitrogen loading (ANL), as local rainfall, in representative shallow, nitrogen limited North Carolina mesohaline estuarine and euhaline coastal Atlantic Ocean habitats. From July 1988 to December 1989, using in situ bioassays, we examined natural phytoplankton growth responses, as¹⁴CO₂ assimilation and chlorophylla production, to rain additions over a range of dilutions mimicking actual input levels. Rainfall at naturally occurring dilutions (0.5 to 5%) stimulated both¹⁴CO₂ assimilation and chlorophylla production, in most cases in a highly significant manner. Parallel nutrient enrichments consistently pointed to nitrogen as the growth stimulating nutrient source. Generally, more acidic rainfall led to greater magnitudes of growth stimulation, especially at lower dilutions. Nutrient analyses of local rainfall from May 1988 to January 1990 indicated an inverse relationship between pH and NO ₃ ^- content. There have been growing concerns regarding increasing coastal and estuarine eutrophication, including ecologically and economically devastating phytoplankton blooms bordering urban and industrial regions of North America, Europe, Japan, and Korea. It appears timely, if not essential, to consider atmospheric nutrient loading in the formulation and implementation of nutrient management strategies aimed at mitigating coastal eutrophication.     

Growth and utilization of internal nitrogen reserves by the giant kelp Macrocystis pyrifera in a low-nitrogen environment

An adult giant kelp plant (Macrocystis pyrifera), moved from an inshore kelp forest to an offshore, low-nitrogen environment near Santa Catalina Island, California (USA), maintained growth for 2 wk on internal nitrogen reserves. Frond elongation rates decreased significantly during the third week, and plant growth rate (wet wt) dropped from an initial inshore rate of 3.6 to 0.9% d^-1. During this 3 wk period, nitrogen contents and free amino acid concentrations decreased, while mannitol and dry contents increased in frond tissues. After depletion of internal nitrogen reserves, the nitrogen content of lamina and stipe tissues averaged 1.1 and 0.7% dry wt, respectively. The experimental plant was exposed to higher ambient nitrogen concentrations during the last 2 wk. Rates of frond elongation and plant growth increased, but nitrogen content and amino acids in frond tissues remained low. Of the total nitrogen contained in frond tissue of the plant before transplantation, 58% was used to support growth in the absence of significant external nitrogen supply. Amino acids constituted a small proportion of these internal nitrogen reserves. Net movement of nitrogen occurred within large fronds, but not between different frond size classes. The nitrogen content of holdfast tissue remained relatively constant at 2.4% dry wt and accounted for 18 to 29% of the total nitrogen. Holdfast nitrogen was not used to support growth of nitrogen-depleted fronds. In comparison to Laminaria longicruris, which is adapted to long seasonal periods of low nitrogen availability, M. pyrifera has small nitrogen-storage capacity. However, internal reserves of M. pyrifera appear adequate to make nitrogen starvation uncommon in southern California kelp forests.     

Separation of Organic Materials and Metallic Elements from Marine Waters by the Operation of Gas-Bubble Extraction

A laboratory experimental investigation was conducted to define the action of rising bubbles with respect to heavy-metal enrichment at the sea surface. Analytical data (HMDE-differential pulse anodic stripping voltammetry technique) show possible enrichments of organic-bound Zn, Cu, Cd and Pb at the top of a laboratory bubble-extraction column filled with water samples collected in the Southern Tyrrhenian Sea. In consideration of analogy between natural and laboratory bubble-extraction processes, laboratory results, i.e., enriched-over-original concentration ratios, make it possible to assess the intrinsic heavy-metal flotation capability in marine waters.     

Separation of Organic Materials and Metallic Elements from Marine Waters by the Operation of Gas-Bubble Extraction

A laboratory experimental investigation was conducted to define the action of rising bubbles with respect to heavy-metal enrichment at the sea surface. Analytical data (HMDE-differential pulse anodic stripping voltammetry technique) show possible enrichments of organic-bound Zn, Cu, Cd and Pb at the top of a laboratory bubble-extraction column filled with water samples collected in the Southern Tyrrhenian Sea. In consideration of analogy between natural and laboratory bubble-extraction processes, laboratory results, i.e., enriched-over-original concentration ratios, make it possible to assess the intrinsic heavy-metal flotation capability in marine waters.     

Behaviour and choice of refuge by voles under predation risk

Animals often show a strong antipredatory response when they are exposed to their most deadly predator. In northern vole populations, the least weasel, Mustela nivalis nivalis, is probably the most important predator of voles. Because of its small size and slender body shape, the least weasel is capable of hunting voles in their burrows. However, small voles can potentially escape weasel predation by selecting holes smaller than those weasels can enter. We studied the choice of nest holes and refuges by two species of voles under simulated predation risk. In a laboratory experiment, voles were provided with four nest boxes as refuges, with individually adjusted entrance sizes. When exposed to the odour of a weasel, voles did not choose the smallest opening; they rather seemed to trade full protection for easy and immediate access by choosing the nest box with an intermediate entrance size. When outside the nest at the time when a weasel entered the arena, voles avoided the refuges with the smallest holes. In addition to using refuges on ground level, voles climbed on top of the boxes as an escape reaction, as well as exhibiting a variety of behavioural responses, such as fast running, freezing and sneaking.Communicated by P.A. Bednekoff     

Elimination of Pentachlorobiphenyls by Nereis virens (Polychaeta) in the Laboratory and the Marine Environment

Fifty sandworms, Nereis virens, were maintained in a closed aquarium system with continuous charcoal filtration at 12°C and 27.6‰ S. They were dosed orally for 10 consecutive days with a mixture of three pentachlorobiphenyls: 35 ng 2,4,6,2',4'-pentachloro[U-¹⁴C]biphenyl, 106 ng 2,4,5,2',5'-pentachlorobiphenyl, and 106 ng 2,3,4,2',5'-pentachlorobiphenyl per g of Nereis virens per day. At the end of the dosing period the accumulated compounds were measured in 5 worms, the remaining 45 specimens were divided into three groups for determining the PCB elimination under different conditions for 14 to 26 weeks: in the laboratory with feeding, in the laboratory without feeding, and in a cage moored in the Weser estuary.

The accumulation percentages for these PCB compounds were 41, 26 and 4% respectively. Times for the initial 50% decrease t_e50 were 4.4, 2.8 and 1.9 weeks respectively, and appeared the same in all three experimental groups. However, in the laboratory experiments the metabolites of the ¹⁴C-labelled compound amounted to ∼60%, compared to the field experiment with ∼30%. This extended the t_e50 for ¹⁴C activity (metabolites included) to ∼9 weeks in the laboratory experiments.     

Potential shift of bacterial community structure and corrosion-related bacteria in drinking water distribution pipeline driven by water source switching

• Bacterial release from aged pipe sections under extreme conditions was quantified. • Released bacterial community structure exhibited large variation after transition. • Risks from transition reduced significantly with cleaner source. As a result of pollution in the present water sources, cities have been forced to utilize cleaner water sources. There are few reports regarding the potential shift of bacterial community structure driven by water source switching, especially that of corrosion-related bacteria. Three types of finished water were used for simulation, the polluted source water from the Qiantang and Dongtiaoxi Rivers (China) was replaced by cleaner water from Qiandao Lake (China). Here, we discussed the transition effects through three simulated reactors. The bacterial characteristics were identified using the high-throughput sequencing and heterotrophic plate count method. It was observed that the level of culturable bacteria declined by 2–3 orders of magnitude after water source switching. The bacterial community released from the pipeline reactor was significantly different under different finished water, and it exhibited large variation at the genus level. Porphyrobacter (58.2%) and Phreatobacter (14.5%) clearly replaced Novosphingobium, Aquabacterium, and Cupriavidus as new dominant genera in system A, which could be attributed to the lower carbon and nitrogen content of the new water source. Although corrosion-inhibiting bacteria decreased after switching, they still maintained dominant in three reactors (6.6%, 15.9%, and 19.7%). Furthermore, potential opportunistic pathogens such as Sphingomonas were detected. Our study shows that after transition to a high quality water source, the total culturable bacteria released was in a downtrend, which leads to a great reduction in the risk of bacterial leakage in the produced drinking water.     

Determination of 4-nonylphenol in carp blood samples by solid phase extraction and chromatographic techniques

In this study, selective methods were developed for isolation, purification, separation and determination of 4-nonylphenol (4NP) in biological samples. Several methods such as high-performance liquid chromatography (HPLC) with fluorescence and diode array detection and gas chromatography coupled to mass spectromotry (GC-MS) are described for the simultaneous determination of 4NP. The nonylphenols in the plasma of fish were extracted through solid phase process by using octadecyl, polymeric and octadecyl endcapping sorbents. The average recoveries in plasma samples spiked with 4NP of levels 1?µg?mL^?1 were between 80–95% using added surrogate standards. The aim of this study was to determine whether trace amounts of 4NP in fish plasma samples could be detected by solid phase extraction and chromatographic methods (HPLC, GC-MS). This technique of monitoring the levels of endocrine-disruptors in plasma samples is consistent, reliable as well as inexpensive.