Effects of nutrient recycling by zooplankton and fish on phytoplankton communities

In laboratory experiments we tested the hypothesis that nutrients supplied by fish and zooplankton affect the structure and dynamics of phytoplankton communities. As expected from their body size differences, fish released nutrients at lower mass-specific rates than Daphnia. On average, these consumers released nutrients at similar N:P ratios, although the ratios released by Daphnia were more variable than those released by fish. Nutrient supply by both fish and Daphnia reduced species richness and diversity of phytoplankton communities and increased algal biomass and dominance. However, nutrient recycling by fish supported a more diverse phytoplankton community than nutrient recycling by Daphnia. We conclude that nutrient recycling by zooplankton and fish have different effects on phytoplankton community structure due to differences in the quality of nutrients released. Received: 21 December 1998 / Accepted: 31 May 1999     

Nutrient dynamics in a floating mat and pond system with special reference to its vegetation

Chemical properties of waters and their seasonal changes were studied in Mizorogaike Pond, a system of pond and floating mat. The following six sites including contrasting habitats and water conditions were monitored to assess nutrient dynamics in the system: 1) a pool on the mat, 2) margin of aSphagnum cuspidatum community, 3) an artificial ‘well’ (water layer beneath the floating mat), 4) aMenyanthes trifoliata community in a hollow, and 5) & 6) two sites in the open water. On the floating mat, the water around theSphagnum community had lower pH values, while that in theM. trifoliata community had higher pH values. This difference was related to the influence of flood water, the extent of which was determined by the microtopography. Seasonal changes in water chemistry on the mat suggested that pond water flooding the mat in late autumn and winter is important for the nutrient supply to the mat surface vegetation in this system. Water chemistry of the ‘well’ suggested that the diffusion of inorganic nitrogen occurs from beneath the peat layer. Two types of cluster analysis based on the mean values for chemical variables and the patterns of fluctuation in these variables were performed. The six sites were classified into similar groups which were identified by water type (pool, hollow, well and open water) by both types of analysis. The results showed that a common kind of perturbation should operate in determining the status of nutrient dynamics in the various water types.     

Impacts of a population outbreak of the urchin Tripneustes gratilla amongst Lord Howe Island coral communities

Subtidal reef surveys within the Lord Howe Island Marine Park revealed that populations of the sea urchin Tripneustes gratilla underwent an explosive outbreak in some regions of the park over a 2-year period. This urchin was rare or absent during 2006 surveys at 33 sites studied, but at sites off northern Lord Howe Island in 2008, densities averaged >1.3 m⁻². Dramatic increases in T. gratilla density (exceeding 4 m⁻²) were observed at some sites. We quantify community-level impacts of T. gratilla using ‘before-after’ and ‘control-impact’ data. Zones closed to fishing exhibited similar increases in T. gratilla density to zones open to fishing. Although not previously reported as a keystone species affecting coral habitat, T. gratilla was found to possess an ‘ecosystem engineer’ function. Outbreak sites were characterised by significant declines in cover of foliose algae, including red algae, which decreased from 11.2% in 2006 compared to 2.5% in 2008. Brown foliose algae also declined at sites where T. gratilla outbreaks occurred, averaging 20.4% in 2006 compared to 1.8% in 2008. By contrast, crustose coralline algal cover increased at sites where high T. gratilla densities were observed, from 2.7% in 2006 to an average of 42.6% in 2008. We found no clear indication of impacts on sessile invertebrates or flow-on effects to other levels of the food web, with no significant change in coral cover or densities of mobile invertebrates or fish populations associated with the T. gratilla outbreak.     

Effects of microhabitat availability on estimates of density of a reef fish: implications for assessments of marine protected areas

Many estimates of ‘marine protected area (MPA) effects’ may be confounded by environmental heterogeneity between MPA and ‘Control’ sites. However, the magnitude and extent of such confounding is generally unknown. Here, the effects of microhabitat availability on estimates of MPA performance were explicitly explored. Abundance of a reef fish species, Ctenochaetus striatus (Quoy & Gaimard, 1825), available microhabitat, and, microhabitat preference for C. striatus within six ‘Ra’ui’ (traditionally managed MPAs) and six paired ‘Control’ sites on the island of Rarotonga, Cook Islands, were estimated. Response ratios accounting for available microhabitat qualitatively modified inferences of Ra’ui effectiveness for two of the six Ra’ui when contrasted with response ratios not accounting for available microhabitat. However, analysis of covariance (ANCOVA) indicated that available microhabitat accounted for significant variation in C. striatus densities between Ra’ui and Control, rather than protection. Our results suggest that adjusting for microhabitat availability may significantly alter our perception of the effects of Ra’ui on C. striatus. Our framework, in concert with our ANCOVA models, provides a stronger assessment of MPA effects. Further, we conclude that metrics of environmental heterogeneity should be incorporated into future assessments of MPA effectiveness, with our work describing one potential framework to accomplish this.     

Effects of Biomanipulation on Fish and Plankton Communities in Ten Eutrophic Lakes of Southern Finland

The effects of biomanipulation were studied in ten Finnish lakes to determine responses in fish and plankton communities and water quality after mass removal of cyprinids. From 1997 to 2001, the fish communities shifted from the dominance of large cyprinids to an explosion of small cyprinids and a higher proportion of piscivores in effectively biomanipulated lakes (>200 kg ha⁻¹ 3 yr⁻¹). The biomass of cyanobacteria decreased, and the duration of the blooms shortened and shifted towards the autumn. Decreased concentrations and slower cycling of nutrients and increased grazing by cladocerans probably affected the declined biomass of cyanobacteria. Less intensive sediment disturbance and increased phosphorus-retention in fast growing fish biomass may have turned the role of the fish assemblage from ‘nutrient recycler’ to ‘nutrient storage’. Increased potential grazing pressure, higher proportion of edible algae, and lower chlorophyll a:total phosphorus ratio indicated strengthened herbivore control. A high mass removal catch in relation to trophic state, low background turbidity, and bearable external loading favoured the successful biomanipulation, whereas intensive cyprinid reproduction, high nutrient loading and non-algal turbidity hindered the recovery. Three important issues should be noticed before biomanipulation in Finland: (1) careful selection of target lake, (2) well-planned, effective and long-lasting biomanipulation and (3) sustainable management of piscivores. An erratum to this article is available at .     

Effects of leguminous ground cover competition on red birch and soil nutrient status in the nursery

Legumes as ground cover are regularly planted to increase nitrogen economy of crops and to improve soil. In the present study various clover species were evaluated as vegetative ground cover in nursery field production of micropropagated red birch (Betula pubescensEhrh. f. rubraUlvinen f. nova) in two 2-year experiments. The clover species and cultivars, Trifolium pratenseL. ‘Bjursele’, T. repens L. ‘Jogeva’, T. repens L. ‘Sonja’, T. hybridum L. ‘Frida’, T. incarnatum L. ‘Opolska’, T. resupinatum L. and T. subterraneum L. were compared to grass sod Festuca rubra L. ‘Ensylva’ and to a coverless ground (control). The last one was kept weed free by hand hoeing. Birch (leaves, stems, branches and roots) and soil nutrient concentrations (N, P, K, Ca, Mg and Fe) were analysed and nutrient ratios in birch determined. The annual clovers, T. incarnatumL., T. resupinatumL. and T. subterraneumL., provided about the same nutrient status in birch as did the control. Perennial clovers and grass were strong competitors with trees. High levels of P and Mg in birch leaves relative to N concentration were typical for poorly growing seedlings. Neither annual nor perennial clovers did generally improve soil nutrient status. This revised version was published online in June 2006 with corrections to the Cover Date.     

Alternate bearing influences annual nutrient consumption and the total nutrient content of mature pistachio trees

The influence of alternate bearing on nutrient utilization and total tree nutrient content was investigated in mature pistachio (Pistacia vera L. cv Kerman trees). Removal of N, P and Zn in fruit and abscised leaves of cropping (‘on’) trees averaged 5, 6, and 2 times, respectively, the removal in abscised leaflets of the non-fruiting, ‘off’ year trees. One hundred and thirty-five kg N, 131 kg K, 86 kg Ca, 39 kg Mg and 18 kg P per hectare were removed in fruits and abscised leaves in ‘on’ year trees. Tree nutrient contents and, presumably, the size of nutrient storage pools in dormant trees varied between ‘on’ and ‘off’ years. There was 22% and 14% more N and P, respectively, in dormant trees following ‘off’ than ‘on’ years. The greater N and P accumulation in ‘off’ year trees is depleted in support of the large fruit demand for N and P during ‘on’ years. In contrast to N and P, there was greater K and Ca accumulation in perennial tree parts during ‘on’ years than during ‘off’ years. The greater K accumulation in perennial tree parts and approximately 30% greater removal of K in annual organs during ‘on’ than ‘off’ years suggests that K uptake could be 4 times higher in ‘on’ year trees than in (non-cropping), ‘off’ year trees.     

Rust mite resistance in apple assessed by quantitative trait loci analysis

The aim of this study was to assess the genetic basis of rust mite (Aculus schlechtendali) resistance in apple (Malus × domestica). A. schlechtendali infestation of apple trees has increased as a consequence of reduced side effects of modern fungicides on rust mites. An analysis of quantitative trait loci (QTLs) was carried out using linkage map data available for F₁ progeny plants of the cultivars ‘Fiesta’ × ‘Discovery’. Apple trees representing 160 different genotypes were surveyed for rust mite infestation, each at three different sites in two consecutive years. The distribution of rust mites on the individual apple genotypes was aggregated and significantly affected by apple genotype and site. We identified two QTLs for A. schlechtendali resistance on linkage group 7 of ‘Fiesta’. The AFLP marker E35M42-0146 (20.2 cM) and the RAPD marker AE10-400 (45.8 cM) were closest positioned to the QTLs and explained between 11.0% and 16.6% of the phenotypic variability. Additionally, putative QTLs on the ‘Discovery’ chromosomes 4, 5 and 8 were detected. The SSR marker Hi03a10 identified to be associated to one of the QTLs (AFLP marker E35M42-0146) was traced back in the ‘Fiesta’ pedigree to the apple cultivar ‘Wagener’. This marker may facilitate the breeding of resistant apple cultivars by marker assisted selection. Furthermore, the genetic background of rust mite resistance in existing cultivars can be evaluated by testing them for the identified SSR marker. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Control of Ixodes scapularis and Amblyomma americanum Through use of the ‘4-poster’ Treatment Device on Deer in Maryland

Deer self-treatment devices (‘4-posters’) were evaluated for their efficacy in reducing populations of blacklegged ticks, Ixodes scapularis, and lone star ticks, Amblyomma americanum. At each of three locations in Maryland, 25 ‘4-posters’ were operated in study areas of approximately 5.18 km². Populations of host-seeking ticks were monitored by flagging of treated areas and similar untreated control areas without ‘4-posters.’ From 1998 to 2002 the percent mortalities achieved were 69, 75.8 and 80 at the three study sites infested with I. scapularis nymphs, and 99.5 and 95.3 for A. americanum nymphs at the two sites where this species occurred. This revised version was published online in July 2006 with corrections to the Cover Date.     

Isobutylidene diurea and other nitrogen fertilizers for seedlings and transplants ofPicea sitchensis in two English forest nurseries

Summary Three slow-release nitrogen fertilizers — medium- and coarse-sized granules of IBDU (isobutylidene diurea) and formalized casein — were applied before sowing or transplanting to Sitka sprucePicea sitchensis, and their effects on growth compared with that on plots not given N or given four topdressings of ‘Nitro-Chalk’ (the source of N used in practice). The comparisons were made at two sites: a very sandy podsol and a sandy loam with better nutrient retention. The experiments with seedlings were continued for four years, those with transplants for three, and the same treatments were applied to the same plots each year. Responses to ‘Nitro-Chalk’ were large, especially during wet seasons. Formalized casein was always as effective as ‘Nitro-Chalk’ for transplants. IBDU (especially the coarse fraction) was almost as good as formalized casein for transplants at both sites and equalled it for seedlings on the sandy loam. For seedlings on the sandy podsol, both particle sizes of IBDU became steadily less effective in succeeding years, and no satisfactory reason can be offered for this decline.     

Impact of sulfur on density of <Emphasis Type="Italic">Tetranychus pacificus</Emphasis> (Acari: Tetranychidae) and <Emphasis Type="Italic">Galendromus occidentalis</Emphasis> (Acari: Phytoseiidae) in a central California vineyard

Sulfur is the oldest and most widely used fungicide in the vineyards of California, where it is used for control of powdery mildew (Uncinula necator [Schw.] Burr). For decades, sulfur use has been associated with outbreaks of Tetranychus pacificus McGregor (Acari: Tetranychidae) on cultivated grapes in the San Joaquin Valley. I undertook large-scale field studies to test this association, to evaluate the impact of sulfur on Galendromus occidentalis (Nesbit) (Acari: Phytoseiidae), a major predator of T. pacificus, and to determine if timing of sulfur applications with respect to grape bloom has an impact on T. pacificus density. The studies took place in a 32 ha vineyard in Fresno County, and all fungicide applications were made with commercial-scale equipment. In 1998 a ‘high sulfur’ treatment, a combination of wettable sulfur and sulfur dust, was compared to ‘low sulfur,’ in which demethylation inhibitor (DMI) fungicides partially substituted for sulfur. In 1999 treatments were ‘sulfur,’ ‘DMI,’ ‘sulfur pre-bloom’ (here sulfur was applied prior to grape bloom, in late May, and then DMIs were applied until mid-season) and ‘sulfur post-bloom’ (the reverse of ‘sulfur pre-bloom’). In each year, the T. pacificus population increase came after the end of fungicide applications, and results clearly show a relationship between sulfur use and T. pacificus density. In 1998, mean T. pacificus density was 2.7 times higher and mean G. occidentalis density 2.5 times higher in ‘high sulfur’ compared to ‘low sulfur.’ In 1999, the highest T. pacificus counts were in the ‘sulfur’ and ‘sulfur pre-bloom’ treatments, 4.8 times higher than ‘sulfur post-bloom’ and 2 times higher than ‘DMIs.’ Density of G. occidentalis was 2.3 times as high in ‘sulfur’ or ‘sulfur pre-bloom’ than ‘DMIs.’ The predator/prey ratio was not significantly different among treatments in 1998, but in 1999 it was highest in the ‘sulfur pre-bloom’ treatment. In 1999, density of Homeopronematus anconai (Baker) (Acari: Tydeidae) was 2.7 times higher in ‘sulfur pre-bloom’ compared to ‘sulfur,’ and higher by 2.7 times in ‘DMI’ compared to ‘sulfur post-bloom,’ suggesting a negative effect of sulfur on this tydeid. These results do not support the hypotheses that the cause of the increase in T. pacificus density is due to negative effects of sulfur on phytoseiids or tydeids. Rather, it appears that a plant-based explanation is likely, first, because of the differences in pre-bloom versus post-bloom sulfuring, and second, because of the long lag time between the end of the sulfur applications and the corresponding increase in spider mite density.     

The effects of harvesting of the South African kelp (Ecklonia maxima) on kelp population structure, growth rate and recruitment

Ecklonia maxima is an economically important kelp in South Africa. The harvested kelp is used mainly as feed for cultured Haliotis midae (abalone) on farms all along the South African South and West Coast. The effects that different harvesting methods have on the growth of sub-canopy kelps, kelp population structure and kelp recruitment were tested in a kelp bed at Bordjies Rif near Cape Town. Two 30 × 10 m sites were set up, about 100 m apart, in near monoculture stands of E. maxima. Each 30×10 m area was subdivided into three treatments. In treatment 1 (T1) the whole ‘head’ of each kelp sporophyte that reached the surface was cut off between the bulb and the primary blade (‘lethal’ method). In treatment 2 (T2) (‘non-lethal’ method), the secondary fronds of all sporophytes that reached the surface were cut 20–30 cm from their junction with the primary blade, and removed. In the control plot, the kelp plants were not treated. Harvesting treatments were done approximately every four months, at low spring tide, from 3 March 2003 to 3 November 2003 (three treatments). The effects of harvesting on the kelps depend largely on the size of plant and the time the fronds were removed; however, no seasonal pattern could be observed. The different treatments had no effect on the growth rate, population structure or recruitment of the kelp. This means that factors other than light play an important role in the growth, structure and recruitment of the kelp beds in False Bay. Results are discussed in relation to current commercial harvesting practices.     

Growth of <Emphasis Type="Italic">Mytilus galloprovincialis</Emphasis> (mollusca,bivalvia) close to fish farms: a case of integrated multi-trophic aquaculture within the Tyrrhenian Sea

A current practice of marine aquaculture is to integrate fish with low-trophic-level organisms (e.g. molluscs and/or algae) during farming to minimise effects of cultivation on the surrounding environment and to potentially increase economic income. This hypothesis has been tested in the present article experimentally, by co-cultivating fish and mussels (Mytilus galloprovincialis) in the field. Integrated multi-trophic aquaculture (IMTA) experiments were started in July 2004 by transplanting mussel seed at two depths (−3 and −9 m) within 1,000 m downstream to fish cages and at 1,000 m upstream from cages. Mussels were cultured in nylon net bags for 12 months and the growth recorded biometrically. The outcome of our field experiment corroborated the idea of IMTA effectiveness. In fact, in the study area, the organic matter from fish-farm biodeposition caused changes in the chemical environment (i.e. controls and impacted sites were significantly different for organic matter availability and chlorophyll-a) and this induced changes in growth performance of co-cultivated mussels. Mussels cultivated close to cages, under direct organic emission, reached a higher total length, weight and biomass than mussel cultivated far from farms.     

Aggressive and Docile Colony Defence Patterns in Apis mellifera. A Retreater–Releaser Concept

Colony defence in Apis mellifera involves a variety of traits ranging from ‘aggressive’ (e.g. entrance guarding, recruitment of flying guards) to ‘docile’ (e.g. retreating into the nest) expression. We tested 11 colonies of three subspecies (capensis, scutellata, carnica) regarding their defensiveness. Each colony was selected as reportedly ‘aggressive’, ‘intermediate’ or ‘docile’ and consisted of about 10,000 bees. We applied three stimulation regimes (mechanical disturbance, exposure to alarm pheromones, and the combination of both) and measured their behaviours by tracking the rates of outflying bees at the entrance sites of the test hives. We provided evidence that for mechanical disturbances the test colonies resolved into two response types, if the ‘immediate’ defence response, assessed in the first minute of stimulation, was taken as a function of foraging: ‘releaser’ colonies allocated flying guards, ‘retreater’ colonies reduced the outside-hive activities. This division was observed irrespective of the subspecies membership and maintained in even roughly changing environmental conditions. However, if pheromone and mechanical stimulation were combined, the variety of colony defensiveness restricted to two further types irrespective of the subspecies membership: six of nine colonies degraded their rate of flying defenders with increasing foraging level, three of the colonies extended their ‘aggressiveness’ by increasing the defender rate with the foraging level. Such ‘super-aggressive’ colonies obviously are able to allocate two separate recruitment pools for foragers and flying defenders.     

Aliens or natives: who are the ‘thugs’ in British woods?

The invasion of native habitats by exotic, or alien, plant species has received considerable attention recently from policy, research, and practical conservation management perspectives. However, a new hypothesis for species dynamics in Britain suggests that a small number of aggressive native plant species (termed ‘thugs’) may have an equal, or greater, impact on native species and habitats than exotic species. Here, we examine this hypothesis using multivariate techniques with field-layer cover data collected during a country-wide survey of British woodlands. Multivariate analysis of these data identified a north-south gradient on the first axis, and that 20 of the 25 National Vegetation Classification woodland types were sampled within the study. The most abundant field-layer species included three of the proposed native ‘thugs’, i.e. Rubus fruticosus, Pteridium aquilinum and Hedera helix in addition to the native woodland indicator species Mercurialis perennis. Variation partitioning was used to compare the relative importance of native field-layer ‘thug’ species with invading alien shrub and tree species relative to other environmental drivers. The variation in the field-layer data-set explained by the three native ‘thug’ species was significant, but they explained a relatively small proportion of the variation relative to other environmental variables (climate, soil, management factors etc.). They did, however, explain almost four times as much variation as the three alien species that were significantly correlated with field-layer species composition (Acer pseudoplatanus, Impatiens glandulifera, Rhododendron ponticum). The results of this analysis suggest that the field-layer of British woodlands is impacted as much by native ‘thug’ species, as it is from ‘aliens’. Concern about the impact of these native ‘thug’ species has been reported previously, but their impact has not previously been compared to the impact of invading aliens. It is hoped that this analysis will do two things, first to act as a sound baseline for assessing any changing balance that should occur in the future, and second, to prompt both ecologists and conservationists to develop woodland management policies based on sound science.     

Subtle ‘boom and bust’ response of <Emphasis Type="Italic">Macquaria ambigua</Emphasis> to flooding in an Australian dryland river

The ecology of dryland rivers is driven by their highly variable hydrology, particularly flooding regimes, whereby intermittent floods typically generate ‘booms’ of primary and secondary productivity, including massive fish production. We tested these concepts in the Moonie River, Australia, using the percichthyid, Macquaria ambigua, a dryland river species known to display pronounced ‘boom and bust’ abundance patterns in response to floodplain inundation followed by extended periods of low to no channel flow. We expected that body condition (as measured by whole body lipid content) and biomass of M. ambigua would be related to prey biomass, and that these factors would all ‘spike’ following widespread flooding. Instead we found more subtle responses. There were ‘booms’ in biomass of Macrobrachium and zooplankton, two important food items, whereas M. ambigua maintained relatively low but sustained lipid and biomass levels following flooding. It appears that instead of a ‘boom’ in fish biomass, abundant invertebrate food resources and sustained lipid levels contributed to high survivorship of this species during the ‘bust’ period over cool dry months.     

Exogenous ethylene influences flower opening of cut roses (<Emphasis Type="Italic">Rosa hybrida</Emphasis>) by regulating the genes encoding ethylene biosynthesis enzymes

The purpose of this paper is to investigate the differential responses of flower opening to ethylene in two cut rose cultivars, ‘Samantha’, whose opening process is promoted, and ‘Kardinal’, whose opening process is inhibited by ethylene. Ethylene production and 1-aminocyclopropane-1-carboxylate (ACC) synthase and oxidase activities were determined first. After ethylene treatment, ethylene production, ACC synthase (ACS) and ACC oxidase (ACO) activities in petals increased and peaked at the earlier stage (stage 3) in ‘Samantha’, and they were much more dramatically enhanced and peaked at the later stage (stage 4) in ‘Kardinal’ than control during vasing. cDNA fragments of three Rh-ACSs and one Rh-ACO genes were cloned and designated as Rh-ACS1, Rh-ACS2, Rh-ACS3 and Rh-ACO1 respectively. Northern blotting analysis revealed that, among three genes of ACS, ethylene-induced expression patterns of Rh-ACS3 gene corresponded to ACS activity and ethylene production in both cultivars. A more dramatic accumulation of Rh-ACS3 mRNA was induced by ethylene in ‘Kardinal’ than that of ‘Samantha’. As an ethylene action inhibitor, STS at concentration of 0.2 mmol/L generally inhibited the expression of Rh-ACSs and Rh-ACO in both cultivars, although it induced the expression of Rh-ACS3 transiently in ‘Kardinal’. Our results suggests that ‘Kardinal’ is more sensitive to ethylene than ‘Samantha’; and the changes of Rh-ACS3 expression caused by ethylene might be related to the acceleration of flower opening in ‘Samantha’ and the inhibition in ‘Kardinal’. Additional results indicated that three Rh-ACSs genes were differentially associated with flower opening and senescence as well as wounding.     

Plant defences and the role of epibiosis in mediating within-plant feeding choices of seagrass consumers

Within-plant variation in susceptibility to herbivory can significantly influence the ecological and evolutionary consequences of plant–herbivore interactions. Seagrasses are marine angiosperms characterised by substantial intra-individual differences in multiple traits, such as nutrients, chemical and structural defences and epibiotic load, all of which can strongly influence herbivore preferences. We quantified the within-plant feeding choices of the two main consumers of the temperate seagrass Posidonia oceanica––the fish Sarpa salpa and the sea urchin Paracentrotus lividus––and determined the plant traits that explained their foraging strategies. We found strong within-plant heterogeneity in both seagrass susceptibility to herbivory and chemical composition, but different consumers exhibited contrasting feeding choices. S. salpa preferred the most nutritious and chemically defended younger leaves, suggesting a full adaptation to consuming this macrophyte and a greater impact of this herbivore on the plant. In contrast, P. lividus consistently preferred the older leaves covered by epibionts, probably attenuating the relative impact of this consumer and helping to explain the weak effects usually recorded for this echinoid in undisturbed meadows. Artificial diet experiments showed that morphology and fine-scale structural defences were the primary determinant of urchin feeding choices, with nutrient content and chemical defences being of secondary importance. Epibiosis did not strongly influence fish feeding, but it did have a strong ‘shared-doom’ effect on urchin consumption. This effect was driven by a distinct preference towards a mixed diet that included both host tissues and their epibiotic community.     

Beta diversity of a Gulf of California rocky-shore fish community

Synopsis Reef fish community composition in three segments of a peninsular rocky shoreline in the Gulf of California was estimated over four periods by visual observation. ‘Point’ and ‘bay’ segments had regular and distinct species compositions over most periods while a ‘middle’ segment was least distinct but consistently had the greatest number of species. Compositional change along the peninsula was least regular during the coldest sea temperature period (April). Mean species turnover between segments was highest between point and bay. Within segments, the point had greater compositional predictable composition (lowest species turnover). When species with regular frequency of encounter were classified into ‘point’, ‘middle’, ‘bay’, and ‘no trend’ groups it was found that comparatively more ‘point’ species had pelagic eggs and comparatively more ‘bay’ species had demersal eggs. Beta diversity of rocky-shore fishes along the physical gradient of the Punta Doble peninsula reflects a transition between exposed and protected rocky shoreline communities. The correlated physical environmental characteristics associated with exposed and protected habitats are discussed in relation to diversity regulation and dispersal strategies in reef fishes.     

Plasmid profiles of bacteriocin-producingLactobacillus isolates from African fermented foods

Fourteen of 200Lactobacillus isolates from African fermented foods,viz. ‘wara’, ‘kenkey’, ‘ugba’, ‘ogi’, ‘kunuzarki’, ‘fufu’ and ‘iru’ were found to produce bacteriocins againstL. plantarum and only three bacteriocinogenic isolates inhibited some of the food pathogens. Plasmid analysis of the 14 bacteriocin-producing lactobacilli showed that only 5 isolates harbored plasmids ranging in size from 3.1 to 55.5 kb.