Threshold response of Madagascar's littoral forest to sea-level rise

Aim Coastal biodiversity hotspots are globally threatened by sea‐level rise. As such it is important to understand how ecosystems resist, respond and adapt to sea‐level rise. Using pollen, geochemistry, charcoal and diatom records in conjunction with previously published palaeoclimatic records, we investigated the mechanism, interactions and ecosystem response and resilience of Madagascar's littoral forest to late Holocene sea‐level rise. Location Sediment sequences were collected along the south‐east coast of Madagascar in two adjacent habitats in Mandena; the highly diverse littoral forest fragment and species‐poor Erica‐matrix. Methods We used a multi‐proxy approach to investigate the relative influence of environmental changes on the littoral ecosystem. We reconstructed past vegetation and fire dynamics over the past 6500 years at two sites in the littoral forest using fossil pollen and macrofossil charcoal contained in sedimentary sequences. Alongside these records we reconstructed past marine transgressions from the same sedimentary sequences using geochemical analyses, and a salinity and drought index through the analysis of fossil diatoms. Results Our findings indicated that it was the synergistic effect of sea‐level rise coupled with rainfall deficits that triggered a threshold event with a switch from two types of littoral forest (an open Uapaca forest and a closed littoral forest fragment) to an Erica–Myrica heath/grassland occurring in approximately less than 100 years. Resilience to sea‐level rise differed in the two adjacent habitats, suggesting that the littoral forest fragment was more resilient to the impacts of sea‐level change and aridity than the open Uapaca woodland. Conclusions We demonstrated that the littoral ecosystem was influenced by late Holocene sea‐level rise and climatic desiccation. While climate change‐integrated conservation strategies address the effects of climate change on species distribution and dispersal, our work suggests that more attention should be paid to the impacts of interactive climatic variables that affect ecosystem thresholds.     

Recent advances and synthesis in biodiversity and biogeography of arenicolous Collembola

Synthesis and new data on interstitial Collembola-fauna in littoral and continental sand sediments. Collembola biodiversity in supralitoral and inland sands can not be compared to the biodiversity developed in mineral soils or leaf litter, and Collembola biodiversity in intertidal sands is lower. The problem of the dispersial of these littoral sand Collembola is considered. A number of species appear have a trans-oceanic dispersal on considerable distances on or in sea water.     

The impact of water-level regulation on littoral macroinvertebrate assemblages in boreal lakes

Regulation of lake water level for power production and flood control is among the major anthropogenic disturbances in boreal aquatic ecosystems. In Finland, over 300 lakes, representing one third of the total inland water area of the country, are artificially regulated. To study the effects of regulation on lake littoral macroinvertebrate communities, samples were taken from upper stony littoral and from lower soft bottom littoral habitats of 11 lakes with different regulation amplitudes (wintertime fall in water level 1.19–6.75 m). Twelve unregulated (wintertime fall in water level 0.11–0.55 m) lakes with otherwise similar characteristics were used as a reference. Non-metric Multidimensional Scaling ordinations showed that the composition of macroinvertebrate assemblages was strongly associated with the amplitude of water level regulation. Taxon richness also decreased with increasing intensity of regulation. Freezing and flushing of sediments in late winter are probably the most important factors leading to the impoverished littoral macroinvertebrate fauna. Invertebrates with long life cycle seem to be particularly vulnerable to unnatural water level fluctuation. Our results show that regulation of water level has a major impact on functionally significant lake littoral macroinvertebrates.     

Behaviour and diet of sea trout post-smolts in a Norwegian fjord system

In order to study the behaviour of sea trout Salmo trutta L., in the early post-smolt phase, reared smolts were tagged with acoustic transmitters and released in the estuary of the River Aurland (Western Norway) and observed for 31–137·5 h. The study was conducted in May-June 1991 and 1995 on a total of seven tagged smolts. The fish moved back and forth along the littoral zone close to the surface and migrated net distances of 100–8000 m. In 1991 the tagged fish were usually observed in schools averaging 24–55 fish, while the tendency to school was less pronounced in 1995. Post-smolts of wild and reared origin were caught by 25 m long gillnets in the littoral zone. In 1991 the mean distance to shore at capture was 4·3 m and the mean depth 0·6 m, and the corresponding numbers in 1995 were 8·0 and 0·8 m. The distribution of the post-smolts is explained by a general preference for shallow water caused by osmoregulatory problems in high-salinity deep water, together with a preference for the sheltered littoral zone and a strong predation pressure in the open sea from fast swimming pelagic fish predators and gulls Larus sp. Schooling seemed to restrict predation by cod Gadus morhua L., in the littoral zone in 1991, while no cod were observed in this habitat in 1995. In both years the stomach contents of the netted fish consisted mainly of terrestrial insects. Reared fish chose prey items similar to those taken by wild fish, but consumed less food.     

Erratum

We studied the structural characteristics of the littoral epilithon in nine lentic water bodies at Hope Bay, Antarctic Peninsula, during summer 2002. At each site we measured the main physical and chemical variables and took epilithic samples for the analysis of dry weigh, ash, ash-free dry weight and chlorophyll a concentration. Distance from the sea of each water body was also considered. One site was selected for sampling lakes and ponds, except for Boeckella lake, where two sampling sites (A and B) were selected due to the heterogeneity of its littoral zone. Three stones for chlorophyll a analysis and another three to estimate dry weight, ash and ash-free dry weight, were taken randomly about 1 m away from the shore-line of each sampling site. Measurements of physical and chemical characteristics were obtained similarly. Water samples for chemical analysis were taken sub-superficially. Lakatoss system of classification and the Autotrophic Index were used to make functional inferences about the epilithic communities. Two PCA analyses were made to classify the water bodies according to environmental features and epilithic variables. In the latter, major patterns in data of epilithon were subsequently interpreted based on environmental data using external validation. Pingüi pond, located in the middle of the penguin rookery, was considered as a passive sample in both PCA analyses due to its extreme characteristics. Limnological features of the studied water bodies were similar to those of other Maritime Antarctic lakes. According to the Lakatoss index, 60% of the sampled lakes had high epilithic mass and a same proportion showed an inorganic type of epilithon The fact that 40% of the water bodies were autotrophic confirmed the importance of benthos as primary producer. According to environmental features, the well-defined groups of lakes emerged from the PCA were mainly determined by distance from the sea, pH, conductivity and salinity, and corresponded to the principal hydrological basins found in the region. Based on the results of the second PCA, littoral epilithon was affected by nitrate concentration and conductivity. In this ordination, water bodies from the same hydrological basin were separated probably as a result of a very complex inter-play of factors with a site-specific response to particular microhabitat characteristics.     

Heavy metals inUlva lactuca collected within Tolo Harbour,an almost landlocked sea

Summary The sea lettuce (Ulva lactuca), a littoral and sublittoral marine macroalga grows abundantly around shorewaters of Hong Kong, especially Tolo Harbour whereU.lactuca is collected from the mudflat for local human consumption as well as for export. Samples ofU.lactuca, together with the ambient seawater and sediment, were collected from several localities around Tolo Harbour, an almost land-locked sea, receiving polluted water from several major streams. For comparison samples were also collected from areas near the unpolluted south coast of Hong Kong Island. It was demonstrated that the samples of seawater and sediment collected within Tolo Harbour were polluted from domestic, agricultural and industrial sources. The extent of the metal (copper, lead, zinc and iron) contamination was further reflected and amplified in the tissue ofU.lactuca.     

Algal structure of the littoral epilithon in lentic water bodies at Hope Bay, Antarctic Peninsula

We studied the composition and density of the algae of the littoral epilithon and the taxa turnover in nine lentic water bodies at Hope Bay, Antarctic Peninsula, during summer 2002. At each site we measured the main physical and chemical variables, and took epilithic samples for the algal analysis. Two composed samples (one for qualitative and one for quantitative analysis) were taken randomly about 1 m away from the shore-line of each sampling site. The morphology of the algal mats could be included in the ‘moat and pond type’ in which Cyanobacteria are well represented. A total of 69 algal taxa were recorded in the whole study area. Chlorophyceae showed the highest taxa richness (33%), followed by Cyanobacteria (29%), Bacillariophyceae (26%), Chrysophyceae (10%), and Tribophyceae (2%). As a result of the redundancy analysis performed, we found that the number, composition, and density of taxa in the water bodies at Hope Bay were strongly influenced by nitrate and suspended solids concentrations and by the distance from the sea. The geographical trend in taxa turnover within Hope Bay was explained by elements from the combination of the metapopulation dynamics and the continuum theories, which are related to dispersal limitation and environmental heterogeneity, respectively.     

The macroinvertebrate fauna of littoral and bottom substrata as a tool for biotypology of Frisian waters

During a biotypological research of surface waters in the province of Friesland, The Netherlands, the macroinvertebrate fauna was sampled, both from the littoral and bottom substrata. Results of this investigation in different types of water on 60 and 55 stations in 1981 and 1982, respectively, are presented. The species richness in the littoral samples exceeded that of the bottom samples, and the samples per station had relatively few species in common. Even in many cases the most abundant taxon was a different one in both samples of the same spot. With multivariate analysis of the data sets from bottom, littoral and total samples a fairly good resemblance was found between these data sets. It is concluded that the semi-quantitative processing of macroinvertebrate fauna data leads to reliable results. One can use one sample per station, wherein different substrata are combined. Distinct clusters were recognized in more extreme environmental conditions such as brackish and acid waters. With the help of the macroinvertebrate fauna the other types of water could not easily be differentiated.     

Water geochemistry and sedimentary pigments in northern Victoria Land lakes,Antarctica

Total concentrations of algal pigments, organic C, C, N, P and S were determined in surface sediments from the littoral zone of 21 lakes in ice-free areas of northern Victoria Land (Antarctica) with different climatic and environmental conditions. Concentrations of major ions and nutrients were also determined in water samples from the same lakes. The latter samples had extremely variable chemical compositions; however, all the lakes resulted oligotrophic. Pigment concentrations in surface sediments were comparable to those reported for other Antarctic lakes and lower than those in oligotrophic lakes at lower latitudes. Cyanophyta, Chlorophyta and Bacillariophyta were the main taxa identified. These taxa correspond to those reported in previous microscopy-based studies on Antarctic phytoplankton and phytobenthos. Discriminant Function Analysis and Canonical Correspondence Analysis of data indicate that the distribution of pigments in these Victoria Land lakes depends mainly on their geographical location (particularly the distance from the sea) and nutrient status.     

Response of macrozoobenthos of lagoon Lake Izmenchivoye (Sakhalin Island) to the discontinuance of water exchange with the sea

Hydrobiological surveys in lagoonal Izmenchivoye Lake (Sakhalin Island) were carried out in 2004, 2005, and 2007 in order to examine the main changes in the composition and structure of macrozoobenthos after the cessation of its communication with the sea. Changes in the hydrological regime of the lake led to a significant reduction in the species list, a decline in the diversity of benthic communities, as well as a twofold increase in the population density of constituent species. The characteristic communities of the seawater cold spreading layer and tidal littoral communities disappeared after the water exchange with the sea ended. The latter communities were replaced with a lacustrine exposed littoral community dominated by amphipods and isopods. The previously shallow-water community dominated by the bivalve Musculista senhousia became the main benthic community. The number of warm-water elements increased markedly. Water temperature proved to be the main factor affecting the composition and structure of benthos of Sakhalin lagoons at the initial stages of evolution of macrobenthos.     

Production and enzymatic decomposition of organic matter by microplankton in a eutrophic lake

This report presents studies on temporal variations of phytoplanktonand bacterioplankton production and the kinetics of bacterialenzyme activity (aminopeptidase, ß-glucosidase andlipase) in the littoral and pelagial sampling sites of a highlyeutrophic lake. Bacterial and algal production correlated wellin pelagic water, but in the littoral there was no significantcorrelation between these processes. The highest activity ofbacterial enzymes occurred during phytoplankton blooms (exceptß-glucosidase). The rates of enzymatic decompositionof organic matter in the littoral and pelagial sampling siteswere similar. Turnover time of enzymatic hydrolysis of the studiedbiopolymers in lake water was the shortest for proteins andlipids during phytoplankton blooms in both sampling sites. Themost dynamic changes in turnover time displayed were for thehydrolysis of polysaccharides by ß-glucosidase inthe littoral samples. The significance of organic matter forbacterial production and enzyme activity, and the role of enzymesin bacterial processing of biopolymers in a lake ecosystem arediscussed     

Comparison of different media for the identification and quantification ofAeromonas spp. in water

In order to assess the suitability of the Starch glutamate ampicillin penicillin-10C agar for the isolation ofAeromonas spp. from waters it was necessary to compare the properties of this medium with those of three others, Starch ampicillin agar, Ampicillin dextrin agar and m-Aeromonas medium, and to monitor different kinds of waters. A selection of forty eight samples were taken from moderately polluted river water, highly polluted river water, polluted sea water (littoral) and treatment & distribution water and monitored using these media. The results were similar with Ampicillin dextrin agar, m-Aeromonas medium and Starch glutamate ampicillin penicillin-10C, but the simplicity of composition and use and its selectivity recommends the last medium as the most adequate for the isolation ofAeromonas spp.Abbreviations ADA ampicillin dextrin agar - mA m-aeromonas medium - SA starch ampicillin agar - SGAP-10C starch glutamate ampicillin penicillin-10C     

Frost formation in the ecotonal zone and its role for release of nutrients

In winter, the littoral substrate of ecotonal zones along north Swedish rivers and lakes freezes. Even if the littoral is flooded at freeze-up, the ice freezes solid to the shore substrate due to low temperature combined with a gradual decrease in water level during winter. Frost conditions were studied during an 8-year period along eight littoral transects in the River Vindelälven and adjacent riverside lagoons. Heavy frost heave with formation of needle ice was observed in several places.Nutrient release was suggested to take place due to the frost process. Sediment was taken to a laboratory experiment where samples with sediment and water were kept under unfrozen and frozen conditions during six months. N (total-N) and Ca were significantly released to the water, while P (total-P) did not show any clear movement from the frozen sediment.The results indicate that frost processes in ecotonal zones are involved in the movement of nutrients between sediment and water.     

Suitability of Taxodium distichum for Afforesting the Littoral Zone of the Three Gorges Reservoir

The littoral zone ecosystem of the Three Gorges Reservoir (TGR) has become significantly degraded by annual cycles of prolonged winter flooding and summer drought. For purposes of flood control and sediment management, the water level in the reservoir is lowered by 30 m during the summer monsoon season and raised again to 175 m above sea level each year at the end of the monsoon period. To explore an effective way to promote biodiversity and associated ecosystem services, we examined Taxodium distichum as a species for afforesting the littoral zone. Sapling growth variations were measured after two rounds of winter flooding. Dominant influence factors were determined by redundancy analysis. Herb community similarities between the experimental afforested areas and nearby control areas were assessed to detect the ecosystem influence of the experimental afforestation. 94.5% of saplings planted at elevations above 168 m survived. All measured growth indices (tree height, diameter at breast height, crown width and foliage density) decreased as the flood depth increased. Completely submerged saplings had a mean dieback height of -0.65 m. Greater initial foliage density led to increased tree height and stem diameter. Shannon-Wiener indices were not significantly different between plots in experimental and control areas, but the low similarity of herb communities between experimental and control areas (0.242 on average) suggested that afforestation would enrich plant community structure and improve littoral zone ecosystem stability. Because littoral zone afforestation provides several ecosystem services (habitat, carbon sink, water purification and landscaping), it is a promising revegetation model for the TGR.     

Environmental Influence on Planktonic Cladocerans and Copepods in the Floodplain of the Upper River Paraná, Brazil

The abundance of microcrustacean species recorded in plankton samples from the littoral and pelagic zones of the Upper Paran River, State of Mato Grosso do Sul, Brazil, was evaluated in relation to abiotic and biotic environmental factors. The cladocerans Bosminopsis deitersi and Bosmina hagmann i were most abundant. The presence or absence of aquatic macrophytes also influenced abundance and species composition. The true zooplankton species were most abundant at the pelagic stations, while species of Chydoridae and Macrothricidae contributed markedly to microcrustacean abundance and species richness at littoral stations. Species abundance was also strongly affected by water level variation. Microcrustaceans, mainly bosminids, were most abundant during low water. During high water, bosminids decreased in abundance while most other species increased. The higher variation of the environmental factors during high water probably explains the shift in abundance patterns. Changes in water level increased mixing of littoral and pelagic microcrustaceans between sampling stations.     

Zooplankton in high-mountain lakes of Altai

In July to August 1999–2001, 53 zooplankton species were recorded in high-mountain lakes of Altai (1800–2400 m above sea level). The abundance of zooplankton varies considerably, but the average values of abundance and biomass are low. According to zooplankton characteristics, the high-mountain lakes are oligotrophic and oligosaprobic. The species composition of the zooplankton community depends on the area and depth of the lakes, and the quantitative indices, particularly in the littoral zone, are determined by water temperature.     

澳门咸潮产生的原因、危害及防治对策

咸潮又称咸潮上溯、盐水入侵,是发生在沿海河口水域的一种水文现象。近年来,澳门咸潮频繁发生,严重影响了人们的正常生活和工作,也为工农业生产带来了巨大的损失。随着咸潮危害的加剧,人们对咸潮的防御对策问题也越来越重视。该论文分析了澳门咸潮产生的原因,认为干旱少雨和海平面上升等自然因素是导致咸潮发生的主要原因,而由人类活动导致的过度用水和生态失衡则加速了咸潮的发生。接着论述了咸潮给澳门带来的危害和测定咸潮的指标方法,最后对预防澳门咸潮的发生提出了一些建议。在澳门的地理背景条件下,除充分利用澳门的水库湖泊资源以增加澳门淡水储备外,更加需要全流域公众珍惜水资源,注意节约用水。     

Diatom assemblages in superficial sediments from the Gulf of Riga,eastern Baltic Sea

Twenty one superficial sediment samples from areas of high and moderate eutrophication in the Gulf of Riga were studied with respect to siliceous microfossils, mainly diatoms.The results seem to imply that the number of taxa and the abundance of the frustules are affected by runoff from rivers and the degree of eutrophication in different parts of the Gulf. Areas with high eutrophication, e.g. the river estuaries, have diatom assemblages of varying composition, while in areas with moderate eutrophication the composition is almost constant and the influx of freshwater diatoms and littoral periphyton small. The high abundance and low diversity of brackish-marine and brackish, planktonic diatoms seem to be a result of an influx of nutrients and pollutants in the water and bottom sediments. The sea ice diatoms occurring in the Baltic waters and also in the Gulf of Riga tend to be resistant to eutrophication or are even favoured by it.     

Towards a ‘Sea‐Level Sensitive’ dynamic model: impact of island ontogeny and glacio‐eustasy on global patterns of marine island biogeography

A synthetic model is presented to enlarge the evolutionary framework of the General Dynamic Model (GDM) and the Glacial Sensitive Model (GSM) of oceanic island biogeography from the terrestrial to the marine realm. The proposed ‘Sea‐Level Sensitive’ dynamic model (SLS) of marine island biogeography integrates historical and ecological biogeography with patterns of glacio‐eustasy, merging concepts from areas as diverse as taxonomy, biogeography, marine biology, volcanology, sedimentology, stratigraphy, palaeontology, geochronology and geomorphology. Fundamental to the SLS model is the dynamic variation of the littoral area of volcanic oceanic islands (defined as the area between the intertidal and the 50‐m isobath) in response to sea‐level oscillations driven by glacial–interglacial cycles. The following questions are considered by means of this revision: (i) what was the impact of (global) glacio‐eustatic sea‐level oscillations, particularly those of the Pleistocene glacial–interglacial episodes, on the littoral marine fauna and flora of volcanic oceanic islands? (ii) What are the main factors that explain the present littoral marine biodiversity on volcanic oceanic islands? (iii) How can differences in historical and ecological biogeography be reconciled, from a marine point of view? These questions are addressed by compiling the bathymetry of 11 Atlantic archipelagos/islands to obtain quantitative data regarding changes in the littoral area based on Pleistocene sea‐level oscillations, from 150 thousand years ago (ka) to the present. Within the framework of a model sensitive to changing sea levels, we discuss the principal factors affecting the geographical range of marine species; the relationships between modes of larval development, dispersal strategies and geographical range; the relationships between times of speciation, modes of larval development, ecological zonation and geographical range; the influence of sea‐surface temperatures and latitude on littoral marine species diversity; the effect of eustatic sea‐level changes and their impact on the littoral marine biota; island marine species–area relationships; and finally, the physical effects of island ontogeny and its associated submarine topography and marine substrate on littoral biota. Based on the SLS dynamic model, we offer a number of predictions for tropical, subtropical and temperate volcanic oceanic islands on how rates of immigration, colonization, in‐situ speciation, local disappearance, and extinction interact and affect the marine biodiversity around islands during glacials and interglacials, thus allowing future testing of the theory.     

Performance of a new chromogenic plating medium for the isolation of Listeria monocytogenes from marine environments

AIMS: This study investigated the performance of a new chromogenic plating medium for the detection of Listeria monocytogenes from naturally contaminated samples obtained from marine environments in Morocco in comparison with the conventional plating media PALCAM and Oxford. METHODS: A total of 479 marine samples (sea water, sediment and mussels) were collected from 16 littoral sites in the region of Agadir (western centre of Morocco). They were examined for the presence of L. monocytogenes using a slight modification of the standardized French method (AFNOR V 08-055) for the detection of L. monocytogenes from food and three different isolation media: PALCAM, Oxford and a new chromogenic plating medium. RESULTS AND SIGNIFICANCE OF THE STUDY: The Oxford and the new chromogenic plating media were found relatively more efficient than the PALCAM medium for the isolation of L. monocytogenes (chi-square test, P < 0.05) from marine samples. However, the new chromogenic plating medium was significantly more selective for L. monocytogenes (P < 0.005) than the two other isolation media as 87.5% of the suspect colonies on this medium were indeed confirmed through identification of the isolates vs 12.7% for Oxford and only 3.8% for the PALCAM medium.