Factors affecting terrestrial movement in the amphibious mangrove rivulus (Kryptolebias marmoratus)

We hypothesised that the exploration tendency of the amphibious mangrove rivulus Kryptolebias marmoratus would be inhibited in the terrestrial environment because of constraints on terrestrial locomotion or orientation. Using a novel object test, we showed that the fish explored objects in the aquatic but not the terrestrial environment, supporting the existence of constraints on terrestrial exploration. In further tests of the effects of extrinsic factors on terrestrial movement between aquatic refuges, shallow water depth simulating desiccation risk and the presence of a conspecific simulating intraspecific competition increased emersion outside of refuges, while high water salinity had no effect. These extrinsic factors had little effect on terrestrial movement between different aquatic refuges, except possibly for the lowest water depth tested. A significant association observed between emersion activity and movement between aquatic refuges suggested that terrestrial movement in K. marmoratus might depend on the tendency of individuals to emerse.     

红树林生长带与潮汐水位关系的研究

根据海南东寨港林市村,廉江车扳镇那肋村,深圳锦锈中华等３个实验点１０条横断面红树林潮滩高程水准测量,林市村潮汐水位观测,潮汐特征水位及浸淹频率分布计算,参照有关港点潮汐实测或预测报资料,确定红树林外边界为平均海面或稍上,内边界（或林内最大高程）为回归潮平均高高潮位（或大潮平均高潮位）对国内外有关报道进行了评述,指出国内许多红树林文献中使用的“高潮位”,“中潮位”“低潮位”用潮汐学术语表述应为“回归     

Dynamics of Sundarban estuarine ecosystem: eutrophication induced threat to mangroves

Background

Sundarbans is the largest chunk of mangrove forest and only tiger mangrove land in the world. Compared to the rich species diversity and uniqueness, very few studies have so far been conducted here, mainly due to its inaccessibility. This study explores water quality, density of biomass, species diversity, phytoplankton abundance and bacterial population of a tidal creek in Sunderban estuary during the post and pre monsoon period of 2008-09.

Results

Phytoplankton community was observed to be dominated by diatoms (Biacillariophyceae) followed by Pyrrophyceae (Dinoflagellates) and Chlorophyceae. A total of 46 taxa belonging to 6 groups were recorded. Other algal groups were Cyanophyceae, Euglenophyceae and Chrysophyceae. Species diversity was highest in summer (March) and lowest in winter season (November) in all the sample stations indicating its close correlation with ambient temperature. Species evenness was fairly high in all five stations throughout the study period. Present study indicated that dissolved oxygen, nutrients and turbidity are the limiting factors for the phytoplankton biomass. The estuary was in eutrophic condition (Chlorophyll-a ≥10 μg/L) in winter. During the month of May phytoplankton biomass declined and at high salinity level (21.2PSU) new phytoplankton species take over, which are definitely better resilient to the high saline environment. Bio-indicator species like Polykrikos schwartzil, Dinophysis norvegica and Prorocentrum concavum points to moderately polluted water quality of the estuary.

Conclusion

Eutrophication as well as presence of toxic Dinoflagellates and Cyanophyceae in the tidal creek of Sundarban estuary definitely revealed the deteriorated status of the water quality. The structure and function of the mangrove food web is unique, driven by both marine and terrestrial components. But little attention has been paid so far to the adaptive responses of mangrove biota to the various disturbances, and now our work unfolds the fact that marine status of Sundarban estuary is highly threatened which in turn will affect the ecology of the mangrove. This study indicates that ecosystem dynamics of the world heritage site Sundarban may facilitate bioinvasion putting a question mark on the sustainability of mangroves.     

Box jellyfish use terrestrial visual cues for navigation

Box jellyfish have an impressive set of 24 eyes of four different types, including eyes structurally similar to those of vertebrates and cephalopods [1, 2]. However, the known visual responses are restricted to simple phototaxis, shadow responses, and object avoidance responses [3-8], and it has been a puzzle why they need such a complex set of eyes. Here we report that medusae of the box jellyfish Tripedalia cystophora are capable of visually guided navigation in mangrove swamps using terrestrial structures seen through the water surface. They detect the mangrove canopy by an eye type that is specialized to peer up through the water surface and that is suspended such that it is constantly looking straight up, irrespective of the orientation of the jellyfish. The visual information is used to navigate to the preferred habitat at the edge of mangrove lagoons.     

Plants and traditional knowledge: An ethnobotanical investigation on Monte Ortobene (Nuoro, Sardinia)

Background

Worldwide there is growing research interest in the ethnobiology of mangrove forests. Notwithstanding that, little information has been published about ethnobiology of mangrove forests in Cameroon. The aims of this study were a) to analyze the harvesting methods and the local selling of mangrove wood products by loggers in the vicinity of Wouri estuary and b) to investigate the patterns of subsistence uses of mangrove wood products around the Douala-Edea reserve.

Methods

Semi-structured interviews were conducted with 120 active mangrove loggers in 23 Douala wood markets and 103 households located in three villages (Mbiako, Yoyo I and Yoyo II) close to Douala-Edea reserve. In each of the three densely populated villages, every second household was chosen for sampling while in all markets, mangrove loggers were chosen randomly. In addition, log diameters were measured in each market using a wooden foldable tape measure. A post hoc analysis (Newman-Keuls test) was performed in order to detect the common wood class diameter sold in the Douala wood markets.

Results

The analysis of the loggers' survey data has shown that large logs of Rhizophora with diameter greater than 40 cm were common in the Douala wood markets and were more closely associated with loggers who used chainsaws. In addition to the general mangroves wood products selling, the analysis on a subsistence level (households' survey) suggests the local population's dependence on mangroves, with multiple uses of Rhizophora racemosa Meyer, R. harrisonii Leechman, Avicennia germinans L. Stearn., Laguncularia racemosa Gaertn. f. and Conocarpus erectus L. timbers for furniture, fences, smoking fish, and fuelwood. Finally, Nypa fruticans (Thunb.) Wurmb. leaves were used as thatching material for house walls and roofs.

Conclusion

Our findings revealed that big logs of Rhizophora were commonly sold by the loggers. A majority of loggers (60%) reported that mangrove marketed wood constitute a principal source of income. Most of the villagers (85.83%) often depend on mangroves for subsistence needs and for them there is no substitute for mangrove wood. Therefore, more efforts should be undertaken at the national level to implement conservation, management and sustainable use of these coastal forests.     

Tiny Is Mighty: Seagrass Beds Have a Large Role in the Export of Organic Material in the Tropical Coastal Zone

Ecosystems in the tropical coastal zone exchange particulate organic matter (POM) with adjacent systems, but differences in this function among ecosystems remain poorly quantified. Seagrass beds are often a relatively small section of this coastal zone, but have a potentially much larger ecological influence than suggested by their surface area. Using stable isotopes as tracers of oceanic, terrestrial, mangrove and seagrass sources, we investigated the origin of particulate organic matter in nine mangrove bays around the island of Phuket (Thailand). We used a linear mixing model based on bulk organic carbon, total nitrogen and δ¹³C and δ¹⁵N and found that oceanic sources dominated suspended particulate organic matter samples along the mangrove-seagrass-ocean gradient. Sediment trap samples showed contributions from four sources oceanic, mangrove forest/terrestrial and seagrass beds where oceanic had the strongest contribution and seagrass beds the smallest. Based on ecosystem area, however, the contribution of suspended particulate organic matter derived from seagrass beds was disproportionally high, relative to the entire area occupied by mangrove forests, the catchment area (terrestrial) and seagrass beds. The contribution from mangrove forests was approximately equal to their surface area, whereas terrestrial contributions to suspended organic matter under contributed compared to their relative catchment area. Interestingly, mangrove forest contribution at 0 m on the transects showed a positive relationship with the exposed frontal width of the mangrove, indicating that mangrove forest exposure to hydrodynamic energy may be a controlling factor in mangrove outwelling. However we found no relationship between seagrass bed contribution and any physical factors, which we measured. Our results indicate that although seagrass beds occupy a relatively small area of the coastal zone, their role in the export of organic matter is disproportional and should be considered in coastal management especially with respect to their importance as a nutrient source for other ecosystems and organisms.     

Ethnobiology, socio-economics and management of mangrove forests: A review

There is growing research interest in the ethnobiology, socio-economics and management of mangrove forests. Coastal residents who use mangroves and their resources may have considerable botanical and ecological knowledgeable about these forests. A wide variety of forest products are harvested in mangroves, especially wood for fuel and construction, tannins and medicines. Although there are exceptions, mangrove forest products are typically harvested in a small-scale and selective manner, with harvesting efforts and impacts concentrated in stands that are closer to settlements and easiest to access (by land or by sea). Mangroves support diverse, local fisheries, and also provide critical nursery habitat and marine productivity which support wider commercial fisheries. These forests also provide valuable ecosystem services that benefit coastal communities, including coastal land stabilization and storm protection. The overlapping of marine and terrestrial resources in mangroves creates tenure ambiguities that complicate management and may induce conflict between competing interests. Mangroves have been cut and cleared extensively to make way for brackish water aquaculture and infrastructure development. More attention is now given to managing remaining forests sustainably and to restoring those degraded from past use. Recent advances in remotely sensed, geo-spatial monitoring provide opportunities for researchers and planners to better understand and improve the management of these unique forested wetlands.     

Gap creation and regenerative processes driving diversity and structure of mangrove ecosystems

Turnover within both mangrove and terrestrial forests is driven by standdevelopment in conjunction with factors influencing tree death andreplacement at various temporal and spatial scales. Development interrestrial forests appears comparable with that in mangroves but turnoverseems to differ considerably between these broad forest types. The mostimportant difference is in the character of small forest gaps. Gaps arecommon in terrestrial forests but those in mangroves rarely involve falls oflarge older trees in the first instance. Instead, mangrove trees usually diestanding in small clusters of mixed age cohorts. Identifying a common causefor gap creation in mangroves might be important towards understandingwhat drives forest turnover but there is a greater need to quantify thisprocess. Small-scale disturbance in mangrove forests is poorly quantified butpreliminary evidence implies that its' importance may have been greatlyunder-estimated. Based on available observations, a conceptual model ofmangrove forest development and gap regeneration is proposed. The modelhelps explain the peculiar characteristics and structure of mangrove forestsand how these forests might respond to changing environmental conditionsand disturbance at various landscape scales.     

Rapid assessments and local knowledge reveal high bird diversity in mangroves of north-west Madagascar

Although the importance of regulating and provisioning services provided by mangroves is widely recognised, our understanding of their role in the maintenance of terrestrial biodiversity is patchy globally and largely lacking for many regions, including conservation priorities such as Madagascar. We carried out the first multi-site bird inventory of mangroves in Madagascar and complemented our data with assessments of local knowledge, in order to broaden our knowledge of which species use this habitat. We directly observed 73 species across three sites in Ambanja and Ambaro Bays, while local respondents indicated the presence of 18 additional species: four observed species are globally threatened, while 37 are endemic to Madagascar or the Malagasy region. Over half the species observed are typically terrestrial, of which 22 have not previously been recorded in mangrove habitats in Madagascar. Local knowledge provided a useful complement to our observed data but we are likely to have underestimated total richness; nevertheless, our findings greatly increased our knowledge of mangrove use by Madagascar’s birds. However, further research is required to investigate the functional role of mangroves in the ecology of the observed species and provide insights into the factors influencing mangrove use.     

The distribution and state of mangroves along the coast of Transkei,Eastern Cape Province,South Africa

The mangrove communities along the coastline of the former Transkei, now part of the Eastern Cape Province, have not been looked at in detail since Ward and Steinkes survey in 1982. Mangroves previously occurred in 17 estuaries but were now found in only 14 of the 76 estuaries visited, with a complete loss of mangroves evident in the Mnyameni, Mzimvubu and Bulungula estuaries amounting to 7.5 ha. Total mangrove loss amounted to 17.6 ha which represents a 6.5% loss over 17 years or 1.04 ha per annum. Tree cover had increased by 16.15 ha in eight other estuaries. This increase could be attributed to the inaccessibility of mangrove stands or to protection afforded by provincial nature reserves and hotel resorts. No new mangrove stands were recorded, although Steinke (pers. comm.) has recently recorded mangroves along the north bank of the Kei River. There has been little change in mangrove species composition in the different estuaries over the past 17 years. Total mangrove loss amounted to 17.6 ha which represents a 6.5% loss over 17 years or 1.04 ha per annum and the species recorded included Avicennia marina, Bruguiera gymnorhiza and Rhizophora mucronata. The mangrove fern Acrostichum aureum L. was recorded for the first time in the Mkozi estuary. Tree density for all estuaries was between 10 and 2594 trees ha^–1. The Mngazana and Mntafufu estuaries had the highest tree densities of 2594 and 1402 trees ha^–1 respectively, typical of riverine mangrove forests. Fringe mangroves were evident in most other systems. Removal of trees for wood has the greatest impact on mangrove cover. Fringe mangrove stands are particularly accessible to harvesters. Only 6% of the current area of trees is afforded some protection in conservation areas. The Mdumbi, Mzamba and Kobonqaba estuaries receive no conservation protection and harvesting has resulted in more than 50% of the trees being removed. The density of dead tree stumps was greater than the number of living trees and no seedlings or juvenile trees were found. Further removal of mangroves within the estuaries south of the Mzimvubu River is expected in the fringe mangroves, as most are unprotected and easily accessible.     

Soil Respiration and Belowground Carbon Allocation in Mangrove Forests

Mangrove forests cover large areas of tropical and subtropical coastlines. They provide a wide range of ecosystem services that includes carbon storage in above- and below ground biomass and in soils. Carbon dioxide (CO₂) emissions from soil, or soil respiration is important in the global carbon budget and is sensitive to increasing global temperature. To understand the magnitude of mangrove soil respiration and the influence of forest structure and temperature on the variation in mangrove soil respiration I assessed soil respiration at eleven mangrove sites, ranging from latitude 27°N to 37°S. Mangrove soil respiration was similar to those observed for terrestrial forest soils. Soil respiration was correlated with leaf area index (LAI) and aboveground net primary production (litterfall), which should aid scaling up to regional and global estimates of soil respiration. Using a carbon balance model, total belowground carbon allocation (TBCA) per unit litterfall was similar in tall mangrove forests as observed in terrestrial forests, but in scrub mangrove forests TBCA per unit litter fall was greater than in terrestrial forests, suggesting mangroves allocate a large proportion of their fixed carbon below ground under unfavorable environmental conditions. The response of soil respiration to soil temperature was not a linear function of temperature. At temperatures below 26°C Q10 of mangrove soil respiration was 2.6, similar to that reported for terrestrial forest soils. However in scrub forests soil respiration declined with increasing soil temperature, largely because of reduced canopy cover and enhanced activity of photosynthetic benthic microbial communities.     

Transitions in ancient inland freshwater resource management in Sri Lanka affect biota and human populations in and around coastal lagoons

The increasing anthropogenic pressure on natural environments results in impacts that affect tropical forest areas and their biodiversity. Adverse impacts on terrestrial and oceanic environments often compound in the intertidal area, where mangrove forest ecosystems thrive. In tropical coastal areas of many developing countries where people depend on wood and other mangrove forest products and services, forest degradation leads to socioeconomic problems. At the same time, increasing freshwater needs in these areas are expected to cause additional problems. On the basis of remote sensing and ground truthing complemented by colonial archival material from the Dutch East India Company (1602-1800), we report that changes to the historic system of inland freshwater management have increased dramatically in recent times. Hydrological changes, such as interbasin transfers, have resulted in a qualitative ecological and socioeconomic degradation in three coastal lagoons in southern Sri Lanka. Variations in river hydrology have caused changes in the areas suitable as mangrove habitat and, thus, have resulted in an altered distribution. However, increases in mangrove area can mask the degradation of the site in terms of floristic composition, significance of the species, and biodiversity (this effect is termed "cryptic ecological degradation"). It is important that such changes be carefully monitored to ensure biological and socioeconomic sustainability.     

Zonation pattern of an isolated mangrove community at Playa Medina,Venezuela

This study focuses on a mangrove system which is completely isolated from the sea, lacking any connecting tidal channels or creeks and far enough from the coastline to prevent tidal flushing. The reason why it has become isolated remains unclear. But it is obvious that this situation may have introduced important changes in soil salinity and hydrological patterns, which might be reflected in the present composition and zonation patterns of the mangrove community. Main findings of this study suggest that: (1) Plant species distribution is affected mainly by water logging and mineral content of soils. (2) Ground water is the only permanent supply of water and salts to the isolated mangrove. (3) Soils are subjected to different degrees of leaching of salts. (4) The K: Na ratios support that mangrove community is not subjected to salinity stress. (5) Continuous leaching of salts favor the advance of terrestrial non-halophytes plants.     

Evolution,ecology and physiology of amphibious killifishes (Cyprinodontiformes)

The order Cyprinodontiformes contains an exceptional diversity of amphibious taxa, including at least 34 species from six families. These cyprinodontiforms often inhabit intertidal or ephemeral habitats characterized by low dissolved oxygen or otherwise poor water quality, conditions that have been hypothesized to drive the evolution of terrestriality. Most of the amphibious species are found in the Rivulidae, Nothobranchiidae and Fundulidae. It is currently unclear whether the pattern of amphibiousness observed in the Cyprinodontiformes is the result of repeated, independent evolutions, or stems from an amphibious common ancestor. Amphibious cyprinodontiforms leave water for a variety of reasons: some species emerse only briefly, to escape predation or capture prey, while others occupy ephemeral habitats by living for months at a time out of water. Fishes able to tolerate months of emersion must maintain respiratory gas exchange, nitrogen excretion and water and salt balance, but to date knowledge of the mechanisms that facilitate homeostasis on land is largely restricted to model species. This review synthesizes the available literature describing amphibious lifestyles in cyprinodontiforms, compares the behavioural and physiological strategies used to exploit the terrestrial environment and suggests directions and ideas for future research.     

Endoglucanase activity in <Emphasis Type="Italic">Neoteredo reynei</Emphasis> (Bivalvia,Teredinidae) digestive organs and its content

Cellulolytic enzymes have been studied in several organisms, such as insects, molluscs and other organisms, which can have enzymes endogenously produced or by symbiotic microorganisms. These enzymes are responsible for breaking down the cellulosic material upon which these organisms feed, probably with the aim of assimilating the sugars and nutrients. As Teredinidae bivalves grown in mangrove trees, this study aimed to measure endo-β-1,4-glucanase activity in different organs and its content. Endo-β-1,4-glucanase activity was detected in different organs of the Teredinidae bivalves, including gills and digestive organs tissues and its content. Moreover, organisms such as teredinids grow up inside wood and this process could perhaps be related to creating growth space. All the endoglucanase extracts, from organs tissues and contents, showed maximum activity at 40 °C. The maximum activity was observed at pH 5.5 for all the extracts, except for intestine tissue, which maximum was at pH 6. Moreover, some of the extracts showed a different profile of the activity as a pH influence, suggesting different distribution of enzymes over the digestive system of the teredinids. The results suggested that the endo-β-1,4-glucanase from Teredinidae could be applied in process that requires low temperature, such as, simultaneous saccharification and fermentation, since it presents lower optimum temperature in comparison to enzymes from terrestrial microorganisms.     

Mosaics in the mangroves: allopatric diversification of tree‐climbing mudwhelks (Gastropoda: Potamididae: Cerithidea) in the Indo‐West Pacific

The Indo‐Australian Archipelago (IAA) is the richest area of biodiversity in the marine realm, yet the processes that generate and maintain this diversity are poorly understood and have hardly been studied in the mangrove biotope. Cerithidea is a genus of marine and brackish‐water snails restricted to mangrove habitats in the Indo‐West Pacific, and its species are believed to have a short pelagic larval life. Using molecular and morphological techniques, we demonstrate the existence of 15 species, reconstruct their phylogeny and plot their geographical ranges. Sister species show a pattern of narrowly allopatric ranges across the IAA, with overlap only between clades that show evidence of ecological differentiation. These allopatric mosaic distributions suggest that speciation may have been driven by isolation during low sea‐level stands, during episodes preceding the Plio‐Pleistocene glaciations. The Makassar Strait forms a biogeographical barrier hindering eastward dispersal, corresponding to part of Wallace's Line in the terrestrial realm. Areas of maximum diversity of mangrove plants and their associated molluscs do not coincide closely. © 2013 The Natural History Museum. Biological Journal of the Linnean Society © 2013 The Linnean Society of London, 2013, 110 , 564–580.     

Long‐term influence of fallen logs on patch formation and their effects under contrasting grazing regimes

Patchiness is a critical functional feature of arid lands, increasing productivity and diversity, but there is little information on the long‐term dynamics of patch formation. While plant‐created heterogeneity is widespread, grazing reduces plant density, hence removing patchiness. Patchiness is also associated with fallen logs and it is particularly important to assess this association in grazed areas, as there are few patches which are not created by living plants. We studied differences in soil nutrient content and soil seed bank associated with the presence of logs in the long ungrazed Koonamore Vegetation Reserve and an adjacent heavily grazed paddock in chenopod shrublands of South Australia. We studied soil properties associated with fallen logs of unknown age, and others known to have persisted for up to 78 years. Logs acted as traps for soil nutrients and seeds. Organic carbon was higher in soils associated with logs, and also higher inside the reserve than in the grazed paddock. Propagule number and species richness were higher next to logs than in open spaces and viable seeds were in much higher abundance next to logs in the grazed paddock than any other site. Increased time in situ of a log had a relatively small effect on soil organic carbon and total nitrogen. Logs act as resource traps which may enhance the diversity of the system, and may be particularly important for maintaining patches of resources in areas of severe grazing damage. Hence, their preservation should be incorporated into management schemes. [Correction added on 3 March 2015, after online publication: The following parts in the abstract have been edited. ‘Organic carbon and total nitrogen were higher in soils associated with logs’ has been corrected to ‘Organic carbon was higher in soils associated with logs’, and ‘had a relatively small effect on soil organic carbon, total nitrogen and available potassium’ has been corrected to ‘had a relatively small effect on soil organic carbon and total nitrogen’.]