Benthic Populations Research Articles

Genomics Observatory Use-Case: The challenge to standardise image and sequence data to Darwin Core format

Genomics Observatory Use-Case: The challenge to standardise image and sequence data to Darwin Core format

Trophic ecology of a blooming jellyfish (Aurelia coerulea) in a Mediterranean coastal lagoon

AbstractThe current lack of knowledge on the trophic ecology of scyphozoans, particularly at the benthic stage, prevents a full understanding of the controls on many jellyfish blooms. The blooming scyphozoan (Aurelia coerulea) completes its entire life cycle in the Thau lagoon (southern France), where the annual population dynamics of both its benthic and pelagic stages have been described. This offered an exceptional framework to investigate the trophic processes regulating jellyfish populations over time. To this aim, stable isotopic signature analysis (δ13C and δ15N) was used to infer the diet of both A. coerulea scyphistomae and medusae over 1 year. These results were matched with medusae gut content analysis and with the monthly abundances of local plankton groups. Lastly, the isotopic signatures of A. coerulea scyphistomae and medusae were compared with those of the oysters (Crassostrea gigas) cultivated in the lagoon to evaluate the potential interspecific trophic competition. The results revealed two seasonal shifts in the trophic niche of A. coerulea and substantial overlap between the diets of its benthic and pelagic stages. Conversely, trophic niche overlaps with the oysters were restricted, suggesting a limited impact of the local jellyfish bloom on shellfish production. Phytoplankton, microzooplankton, mesozooplankton, and sedimentary organic matter were all important food sources during critical periods of A. coerulea life‐cycle. However, microzooplankton abundance was found to be key for the production of buds by the scyphistomae and, therefore it is likely to control the benthic population size and, thereby, to modulate the intensity of its annual bloom in Thau.

Cross-scale connectivity of macrobenthic communities in a patchy network of habitats: The Mesophotic Biogenic Habitats of the Northern Adriatic Sea

Connectivity is a fundamental ecological property affecting stability, resilience and recovery of marine populations, in particular in networks of patchy habitats as the Mesophotic Biogenic Habitats of the Northern Adriatic Sea. Specific information on the dispersal behaviour of many species living in these habitats is lacking, thus the connectivity simulations were performed over different pelagic propagules duration and different reproductive seasons of six consecutive years, covering most of the possible dispersal behaviour variability. The connectivity simulations were analysed with graph analysis methods by characterizing each connectivity graph with several structural measures and by identifying sites with greatest individual and group centrality. We tested the hypothesis that geographic proximity of sites cannot be a proxy for the connectivity and that hydrodynamic connectivity is statistically significantly related to the observed beta diversity among the studied sites. Results showed that species with different pelagic propagules duration follow greatly different dispersal dynamics, and that the network of studied outcrops is only partially connected to coastal benthic populations. Our results also made possible a critical appraisal of the current conservation strategies, evidencing gaps in the existing network of protected Mesophotic Biogenic Habitats in the Northern Adriatic Sea. We suggest possible improvements for an efficient preservation strategy of these unique biodiversity hotspots by including a fundamental ecological process, the dispersal connectivity, into the process of decision making for conservation.

Analysis of a reaction-diffusion benthic-drift model with strong Allee effect growth

The dynamics of a reaction-diffusion-advection benthic-drift population model that links changes in the flow regime and habitat availability with population dynamics is studied. In the model, the stream is divided into drift zone and benthic zone, and the population is divided into two interacting compartments, individuals residing in the benthic zone and individuals dispersing in the drift zone. The benthic population growth is assumed to be of strong Allee effect type. The influence of flow speed and individual transfer rates between zones on the population persistence and extinction is considered, and the criteria of population persistence or extinction are formulated and proved.

Limited Genetic Connectivity Among Sargassum horneri (Phaeophyceae) Populations in the Chinese Marginal Seas Despite Their high Dispersal Capacity.

Sargassum horneri is a habitat-forming species in the Northwest Pacific and an important contributor to seaweed rafts. In this study, 131 benthic samples and 156 floating samples were collected in the Yellow Sea and East China Sea (ECS) to test the effects of seaweed rafts on population structure and connectivity. Our results revealed high levels of genetic diversity in both benthic and floating samples based on concatenated mitochondrial markers (rpl5-rps3, rnl-atp9, and cob-cox2). Phylogenetic analyses consistently supported the existence of two lineages (lineages I and II), with divergence dating to c. 0.692Mya (95% HPD: 0.255-1.841 Mya), indicating that long-term isolation may have occurred during the mid-Pleistocene (0.126-0.781Mya). Extended Bayesian skyline plots demonstrated a constant population size over time in lineage I and slight demographic expansion in lineage II. Both lineages were found in each marginal sea (including both benthic and floating samples), but PCoA, FST , and AMOVA analyses consistently revealed deep genetic variation between regions. Highly structured phylogeographic pattern supports limited genetic connectivity between regions. IMA analyses demonstrated that asymmetric gene flow between benthic populations in the North Yellow Sea (NYS) and ECS was extremely low (ECS→NYS, 2Nm=0.6), implying that high dispersal capacity cannot be assumed to lead to widespread population connectivity, even without dispersal barriers. In addition, there were only a few shared haplotypes between benthic and floating samples, suggesting the existence of hidden donors for the floating masses in the Chinese marginal seas.

Macrobenthic community structure of the Mhlathuze Estuary, a permanently open estuarine embayment in KwaZulu-Natal, South Africa

The Mhlathuze Estuary, an estuarine embayment in northern Zululand, is considered an estuary of national conservation importance. No historical data on the benthic macrofauna are available for the past 20 years, creating a significant gap in our understanding of the ecology and benthic assemblage of this system. The primary aim of this study was to provide updated information on the ecology of the macrobenthic community. Benthic samples were collected quarterly using a Zabalocki grab during the period 2016–2017. The 87 taxa recorded were largely dominated by the tanaid Halmyrapseudes cooperi, followed by the brachyuran crab, Paratylodiplax blephariskios and the amphipod Grandierella bonnieroides. A multivariate data analysis was performed and PERMANOVA results indicated significant differences (p < 0.05) between sites in number of taxa, species diversity and density. A stable system with limited seasonal influences and the effect of May 2017 flood were highlighted in the study. The 100 benthic taxa recorded in previous studies, of which 46 species are still present, suggests a marked decline in macrobenthic diversity and a change in community, possibly linked to reduced freshwater inflow and agricultural effluent. The continuing ecological relevance of this protected area relies on reducing catchment activities that are detrimental in sustaining benthic populations.

Structure of benthic macroinvertebrates population in an area of Mopoyem Bay (Ebrie Lagoon, Côte d'Ivoire) exposed to the discharge of a fish farm effluents.

Discharges of untreated effluent from fish farming into the aquatic environment are a practice that can affect local biodiversity. This study was conducted to characterize, in the Ebrie Lagoon, the structure of benthic macroinvertebrates inhabiting an environment exposed to effluent discharges from fish farms. The benthic macroinvertebrates were collected with a Van Veen grab seasonally between August 2016 and July 2017 at the effluent discharge point in the lagoon and at a reference station out of anthropogenic activities. Identification of organisms was done using specialized keys. The results revealed that the proportion of tolerant macroinvertebrates is relatively high (47.74%) at the point of discharge of fish farming effluents into the Ebrie Lagoon. While at the reference station, macroinvertebrates population is dominated by sensitive and medium-sensitive taxa (93.53%). The benthic macroinvertebrates population, influenced by seasonal variations, exhibits peaks of abundance and diversity during the rainy seasons, while during the dry seasons, they strongly decline. Fish farming effluents dumped in Ebrie Lagoon lead to structural modifications of the local benthic macroinvertebrates population. These disturbances are intensified in dry seasons and attenuated in rainy seasons. This information should be taken into account in any decision to promote the responsible practice of fish farming and the sustainable management of water resources exploited for fish farming purposes.

An anomalous bi-macroalgal bloom caused by Ulva and Sargassum seaweeds during spring to summer of 2017 in the western Yellow Sea, China

An unprecedented bi-macroalgal bloom caused by Ulva prolifera and Sargassum horneri occurred from spring to summer of 2017 in the western Yellow Sea (YS) of China, where annual large-scale green tides have prevailed for a decade. The distinct genesis and blooming dynamics of the two seaweed species were detected and described. Unlike the consistent raft-origin of the floating Ulva biomass, the massive pelagic S. horneri was derived from multiple sources (residual seaweeds from the previous winter bloom and those drifting from offshore water in the south). The scale of the green tide in 2017 was found smaller than the previous four years. We then discussed a number of hypotheses attributing to this reduction, including reduced epiphytic green algae from aquaculture rafts and the influences of the massive pelagic S. horneri. However, further research is needed to identify the origin of the pelagic S. horneri in the western YS and any affiliations with the benthic populations, and to elucidate the interactions of this species with the annual green tides and the ensuing consequences.

Changes in Odonata abundance between 2000 and 2015–2016 in Saga Plain, northern Kyushu, Japan

The impacts of systemic pesticides on biodiversity are a major ecological concern. Rapid population declines of Sympetrum species (Odonata: Libellulidae) have been reported in various localities in Japan beginning in the 2000s. Several studies suggested that nursery box use of fipronil in paddy fields to prevent insect feeding on rice seedlings negatively impacts Sympetrum larvae. Although several other Odonata species are suspected to have declined significantly in recent decades, accurate evaluations of their population declines and identification of the causes are difficult due to limited data on population density prior to the declines. In addition, a recent study revealed that herbicide use negatively affects phytophilous species, but positively impacts benthic populations of lentic Odonata by reducing the prevalence of macrophytes. To evaluate the changes in the abundance of Odonata during recent decades, we conducted line transect observation of Odonata populations at one site along the Tafusegawa River in Saga Plain, northern Kyushu, Japan in 2000 and 2015–2016, before and after the use of fipronil in paddy fields in this area. We identified that Sympetrum eroticum eroticum (Selys) (Libellulidae) populations have significantly decreased in recent years. In addition, prevalence of a lotic benthic species, Asiagomphus pryeri (Selys) (Gomphidae), has significantly decreased in this time period. Other lotic benthic species have also declined in this area, suggesting that benthic environments might have degraded in recent years. In contrast to the decrease of the abovementioned species, prevalence of the lentic and benthic species Orthetrum melania melania (Selys) and Rhyothemis fuliginosa Selys (Libellulidae) (Libellulidae) significantly increased. The densities of lentic phytophilous species appear to have decreased, suggesting that reduction of macrophytes in surrounding lentic environments could be involved in these changes.

Attempted use of an uncommon bay scallop color morph for tracking the contribution of restoration efforts to population recovery

In our ongoing bay scallop restoration efforts in eastern Long Island, NY, United States, we have planted millions of hatchery‐reared juveniles to serve as broodstock when they mature. These plantings have driven the resurgence of larval recruitment, benthic population sizes, and commercial fishery landings over a 12‐year period. In this article, we detail an attempt to track the contribution of our restoration efforts to population rebuilding using planted “skunks,” an uncommon color morph, by looking for increased skunk frequencies in subsequent wild cohorts. Although we saw higher skunk frequencies among large juveniles in natural populations in the first 3 years after extensive skunk plantings, supporting use of uncommon color morphs as a passive tracer, this conclusion was not supported when examined over a 12‐year period, as no strong correlations were seen between skunk frequencies at different life stages (adult broodstock, small and large F1 juveniles, F1 adults) for respective cohorts. Potential reasons for poor correlation between skunk frequencies and restoration efforts include lower than expected production of skunk offspring, dilution of out‐planted contribution to growing natural populations, interannual variability in skunk frequencies that may have obscured the expected skunk signal, and/or differentially higher mortality of skunks at postset and larger juvenile stages. In the latter case, skunks experienced higher overwinter mortality, most likely due to predation, in 9 of 11 years. This led us to suspend skunk plantings after 3 years. Nevertheless, commercial fishermen perceived skunks to be “our” scallops, helping raise the profile of and support for our restoration efforts.

Spirostomum teres: A Long Term Study of an Anoxic-Hypolimnion Population Feeding upon Photosynthesizing Microorganisms

The pelagic / anoxic hypolimnion population of Spirostomum teres was investigated as a part of the long-term ciliates’ monitoring (2003–2016) in an oligo- to mesotrophic monomictic hyposaline crater lake Alchichica (Puebla / Veracruz, Mexico), including an analysis of picoplankton (both heterotrophic, HPP and autotrophic, APP) and inorganic compounds of nitrogen (ammonium, nitrite, nitrate), phosphorus (dissolved reactive phosphorus, DRP) and silicon. Additionally, detailed studies of the ciliate vertical distribution and feeding activity measured upon fluorescently labelled APP (picocyanobacteria) were carried out. The results were compared with those from a neighbour freshwater crater lake La Preciosa and with a meromictic karstic lake La Cruz (Cuenca, Spain). The ciliate vertical distribution within the water column was very well defined: During the first decade, the benthic population was frequently found throughout a developing stratification of the lake. The established stratification of the lake turned the conditions favourable for the formation of an oxycline / hypolimnion population, typically, several meters below the deep chlorophyll maximum (formed basically by diatoms); the population preferred the layers without detectable dissolved oxygen. However, an observed gradient of light (PAR) could support both oxygenic and anoxygenic photosynthesis. Late stratification after deepening of the thermocline reduced the layers with S. teres population to a minimum apparently due to the drastic change in physicochemical conditions within a metalimnion, coupled with an oxycline, and limited to 1 to 2 meters; microstratification was found. Last years, the very bottom population disappeared or it was reduced and the late stratification S. teres peaks were smaller or did not appeared. Generally, S. teres oxycline / anoxic hypolimnion population was observed from June through November. Optimum picoplankton numbers in conditions that supported the ciliate growth were found: The ciliate was peaking at APP of 0.6 to 1 × 105 cells mL–1; the optimum of HPP was observed round 1.4 × 106 cells mL–1. S. teres was efficiently feeding upon picocyanobacteria in numbers of 105 cells mL–1 reaching the clearance rate of 2000 nL cell–1h–1, which represented in average 130 to 210 cells cell–1h–1 ingested. Feeding upon purple sulphur bacteria was observed but only during the end of the lake stable stratification when the ciliate population was already dropping. On the other hand, the volume specific clearance of S. teres upon picocyanobacteria (103 h–1) did not support the hypothesis that they could serve as a sole prey. Feeding upon eukaryote phytoplankton (chlorophytes Monoraphidium minutum, diatoms Cyclotella choc tawhatcheeana) could be of higher importance that previously supposed. Additionally, a use of ingested and retained photosynthetic prokaryotes is hypothesized.

Benthos population in seagrass ecosystem at Bira Island Kepulauan Seribu, Jakarta Indonesia

One group of organisms that can be used as bio indicators of water quality is benthos, these organisms are spread over several habitats and also in coastal areas, one of which is in the seagrass ecosystem on Bira Island, located in the Kepulauan Seribu Jakarta. The aim of this study was to determine the dynamics of benthic population as an illustration of the environmental conditions on Bira Island for 6 months of observation. The method used in this study was descriptive with survey design. Data collecting by purposive sampling with the transect method at 3 observation stations. The data were analyzed descriptively through the calculation of abundance, diversity and dominance. The results of the study identified 23 species of benthos included in the 3 phylum with the largest to lowest composition represented by molluscs, arthropods and echinoderms phylum. The benthic population fluctuates and shows a pattern of decreasing trends every month during observation. The abundance of the highest species of each phylum is represented by Turicula javana (Mollusc), Portunus sp (Arthropods) and Holothuria atra (Echinoderms). The Species Abundance based on the observation station shows that the highest abundance is at station 1, followed by station 2 and the lowest is station 3. Benthos diversity at each station is in the moderate category, and there is no species dominates.

Connections Between Benthic Populations and Local Strandings of the Southern Bull Kelp Durvillaea Antarctica Along the Continental Coast of Chile1.

Floating seaweeds are important dispersal vectors in marine ecosystems. However, the relationship between benthic populations and stranded seaweeds has received little attention. After detachment, a fraction of floating specimens returns to the shore, resulting in strandings that fluctuate in space and time. It has been hypothesized that the availability of stranded seaweeds is related to their benthic abundance on adjacent coasts. Using the large fucoid Durvillaea antarctica, we tested whether stranded biomasses are higher at sites with dense adjacent benthic populations. Benthic abundance of D.antarctica along the continental coast of Chile was estimated using three approximations: (i) availability of potentially suitable habitat (PSH), (ii) categorical visual abundance estimates in the field, and (iii) abundance measurements in the intertidal zone. Higher PSH for D.antarctica was observed between 31°S-32°S and 40°S-42°S than between 33°S and 39°S. Lowest benthic biomasses were estimated for the northern latitudes (31°S-32°S). Regression models showed that the association between stranded biomass and PSH was highest when only the extent of rocky shore 10km to the south of each beach was included, suggesting relatively short-distance dispersal and asymmetrical transport of floating kelps, which is further supported by low proportions of rafts with Lepas spp. (indicator of rafting). The results indicate that stranded biomasses are mostly subsidized by nearby benthic populations, which can partly explain the low genetic connectivity among populations in the study region. Future studies should also incorporate other local factors (e.g., winds, currents, wave-exposure) that influence stranding dynamics.

Unravelling the population dynamics of the Mediterranean bryozoan Pentapora fascialis to assess its role as an indicator of recreational diving for adaptive management of marine protected areas

Marine Protected Areas (MPAs) have been recognized as effective management and conservation tools to protect marine coastal ecosystems. However, due to an increasing interest in marine ecosystems, recreational activities such as scuba diving are rapidly growing in these areas, highlighting the need to implement adaptive management strategies based on continuous monitoring and evaluation of protected areas. To date, several studies have quantified the impact of diving using benthic species as indicators, such as bryozoans, but usually ignoring their population dynamics. Here, we studied the population dynamics of the abundant and common bryozoan Pentapora fascialis on a Mediterranean MPA with high levels of diving activity. Specifically, we monitored eight different localities with two different levels of diving frequentation (non-frequented versus frequented) from October 2015 to October 2018, accounting for the demographic parameters before and after the summer. Our results showed the impact of diving on the density, recruitment, survival, and size of colonies, reaching higher values on non-frequented localities. In addition, we detected two peaks of recruitment during July 2016 and July 2018, suggesting that bryozoan recruitment events are stochastic, with a high inter-annual variation. Contrastingly, regardless of the diver frequentation level, we found higher growth rates during the colder months and higher necrosis rates after the summer in all the studied localities. Besides the aforementioned differences, the densities observed in this study were much higher compared to previous studies performed in the same area during the 1990s. Taken together, these results suggested rapid population dynamics of P. fascialis, with fast growth rates and a high capacity to recover from perturbations. Despite the quantified effects of diving on our studied species, their abundance in frequented sites remained very low over the whole study period, compromising the use of P. fascialis as an optimal indicator of diving impact for adaptive management of temperate benthic populations. Overall, our results highlight the importance of continuous monitoring programs to unravel the population dynamics of indicator species to effectively manage marine populations and evaluate the impact of human activities on marine protected areas.

Assessment of the genetic relationship between the recently established benthic population and the adjacent floating populations of Sargassum horneri (Phaeophyceae) in Dalian of China by newly developed trinucleotide microsatellite markers

Sargassum horneri is a conspicuous canopy-forming brown seaweed growing on solid substrates or floating on sea surface. A recently established benthic population was discovered in a bay in Dalian, China, in 2016 and suggested to be derived from the earlier floating population. Since 2016, floating populations have kept appearing in the adjacent area. The genetic connectivity between this recently established benthic population and the adjacent floating populations remains unclear. In this study, 10 novel informative trinucleotide microsatellite markers were developed through the high throughput sequencing technology, and employed to analyze the genetic structure of the benthic population (DS16 and DS18) and three adjacent floating populations (DL16, BL16, and DL18) sampled in 2016 and 2018, with one floating population collected from Shidao in 2016 (SD16) as reference. Significant genetic differentiation was found to exist between the benthic and floating populations, and among floating populations from different years. Almost no membership of floating populations was detected in the benthic population and vice versa by the Bayesian model–based structure analysis, indicating very limited genetic connectivity between them. Significant excess of heterozygosity, significant multilocus linkage disequilibrium, high frequency of repeated genotypes, and putative clones were detected in all floating populations, indicating that asexual reproduction is likely dominant in them. Inbreeding and founder effect were revealed to be present in the benthic population. Further studies will focus on tracking the dynamics of genetic structure in the recently established benthic population and investigating the exact reproductive means and patterns of floating populations.

Eastern oysters use predation risk cues in larval settlement decisions and juvenile inducible morphological defenses

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 621:83-94 (2019) - DOI: https://doi.org/10.3354/meps12998 Eastern oysters use predation risk cues in larval settlement decisions and juvenile inducible morphological defenses Jessica L. Pruett*, Marc J. Weissburg School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA *Corresponding author: jpruett7@gatech.edu ABSTRACT: Predation is an important factor affecting the recruitment of marine benthic populations. Larvae can reduce their risk of predation by avoiding settlement near predators, whereas juveniles can resist predation through induced morphological defenses. We performed a 2 mo field study to understand the nature of the predation risk cues used by settling eastern oyster larvae and developing juveniles to decrease predation threat during recruitment. We found that oyster recruitment was highest on caged tiles near juvenile oysters, but lowest on tiles near active mud crab predators that produce a combination of predator metabolites and crushed conspecific alarm cues. Chemical cues from crushed conspecifics alone did not affect recruitment in the field, yet oyster larvae avoided either mud crab cues or crushed conspecific cues when presented separately in lab behavior experiments. Comparing the field to lab results suggests alarm cues may be unreliable under natural environmental conditions or were not present at high enough concentrations in the relatively high turbulent flow environment of our field site to convey the predation threat necessary to deter oyster settlement. Oyster spat grew most quickly when exposed to crushed conspecifics and may employ different strategies in response to unique risk cues or predation risk levels by avoiding settlement near actively feeding future predators but growing quickly to reach a size refuge in the presence of alarm cues. These non-consumptive predator effects at different life stages may have important demographic consequences for oyster populations that need to be considered in conjunction with predator consumptive effects. KEY WORDS: Alarm cue · Crassostrea virginica · Non-consumptive effect · Panopeus herbstii · Phenotypic plasticity · Predation risk · Settlement cue Full text in pdf format PreviousNextCite this article as: Pruett JL, Weissburg MJ (2019) Eastern oysters use predation risk cues in larval settlement decisions and juvenile inducible morphological defenses. Mar Ecol Prog Ser 621:83-94. https://doi.org/10.3354/meps12998 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 621. Online publication date: July 04, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

The origin and population genetic structure of the \u2018golden tide\u2019 seaweeds, Sargassum horneri, in Korean waters

In recent years, drifting and inundating brown seaweed (Sargassum horneri) biomass, called ‘golden tides’, has frequently drifted and accumulated along the southern coastlines of Korea, causing devastating impacts on the local economy and coastal ecosystems. In this study, based on combined analyses of mitochondrial DNA cox3 gene and seven microsatellites, we investigated the genetic makeup of the floating S. horneri populations (N = 14) in comparison to Korean benthic populations (N = 5), and tracked their genetic sources. Given a shared mtDNA haplotype and oceanic circulation systems, the floating populations may have been originated from the southeastern coast of China (e.g. Zhoushan, Zhejiang province). Population structure analyses with microsatellites revealed two distinct genetic clusters, each comprising floating and benthic populations. High levels of inter-population differentiation were detected within Korean benthic samples. The floating populations from the same periods during a 2015–2018 year were genetically more different from one another than those from different periods. These results suggest that the floating populations might be of multiple genetic sources within geographic origin(s). This study will inform management efforts including the development of “S. horneri blooming forecasting system”, which will assist in mitigating ecological and economic damages on the Korean coastal ecosystems in the future.

Density of benthic macroalgae in the intertidal zone varies with surf zone hydrodynamics

ABSTRACTSurf zone hydrodynamics influence subsidies (larval settlers and phytoplankton food) to the intertidal zone; subsidies have been observed to be much higher at more dissipative shores compared to reflective shores. Benthic macroalgal populations may be favoured at more reflective surf zones due to slower water exchange with the coastal ocean, facilitating retention of spores. In addition, larval invertebrate settlers are far less abundant at more reflective surf zones, and benthic macroalgae may experience lower competition from sessile invertebrates for space. We used surf zone width as an indictor of surf zone hydrodynamics; surf zones are wider at more dissipative surf zones compared to reflective surf zones. We tested the hypothesis that as surf zone width increases, macroalgal density would decrease. We used aerial near-infrared and visible light images to calculate the normalised difference vegetation index (NDVI) at eight intertidal sites along the Oregon coast and compared NDVI with algal biomass (dry and wet weight per square metre) at each specific location; linear regressions between NDVI and dry and wet algal biomass were significant (P < 0.01); NDVI was an accurate indicator of macroalgal density. Surf zone width was measured using Google Earth images. NDVI and dry and wet algal biomass were significantly lower at wider surf zones (P < 0.01). Although the mechanism underlying this relationship is unknown, the intertidal macroalgal community clearly varied with surf zone hydrodynamics as indicated by surf zone width.

Characteristics of geochemical fractions of phosphorus and its bioavailability in sediments of a largest brackish water lake, South Asia

The spatio-temporal distribution of geochemical fractions of phosphorus and its bio-availability for Asia's largest brackish water lake has been carried out. One way ANOVA analysis revealed that both iron bound phosphorus (Fe-P) (p<0.05, n=360) and calcium bound phosphorus (Ca-P) (p<0.05, n=360) showed a significant variation on a spatio-temporal scale which may be attributed to pH and salinity of overlying water column. Pearson's correlation matrix revealed that sediment texture played a major role in the quantification of phosphorus species. The relationship between Ca-P and Ca was not established for the sediments of the lake Chilika, which suggested its authigenic origin. The concentration of bio-available phosphorus (BAP) in different sectors of the lake varied in the order of northern sector (45.64%)>central sector (42.22%)>outer channel (36.63%)>southern sector (29.27%) of total phosphorus (TP). This is supported by the fact that bioavailable P is comparatively higher in the freshwater zone than in the brackish water zone. The principal component analysis (PCA) revealed a good relationship between dissolved phosphate concentrations of water column with benthic population density. It showed that TP availability in the sediment of the lake is mostly bounded with Al, Fe and organic matter (OM). Positive association of total carbon (TC), total nitrogen (TN) and OM with negatively loading of Eh indicates towards the fact that, deposition of TN and TC is largely governed by OM availability in sediment.

Replicated evolutionary inhibition of a complex ancestral behaviour in an adaptive radiation.

Adaptive radiations often exhibit high levels of phenotypic replication, a phenomenon that can be explained by selection on standing variation in repeatedly divergent environments or by the influence of ancestral plasticity on selection in divergent environments. Here, we offer the first evidence that plastic loss of expression of a complex display in a novel environment, followed by selection against expression, could lead to replicated evolutionary inhibition of the phenotype. In both ancestral (oceanic) and benthic (freshwater) populations of the threespine stickleback fish, cannibalism is common and males defending nests respond to approaching groups with a complex diversionary display. This display is not exhibited by males in allopatric, limnetic (freshwater) populations from which cannibalistic groups are absent. Laboratory-reared males from three limnetic populations exhibit a reduced tendency to respond to cannibalistic foraging groups relative to laboratory-reared ancestral and benthic males, but still are capable of producing a similar array of forms of the display despite many generations of disuse. Thus, replication in adaptive radiations can reflect reduced expression of an ancestral trait followed by evolutionary inhibition while the population retains the capacity to express the trait under extreme ancestral conditions.