The interplay between mangroves and saltmarshes at the transition between temperate and subtropical climate in Florida

The interplay between mangroves and saltmarshes at the temperate to subtropical transition in Florida results in dramatic changes to the appearance of the coastal landscape. In the 1980s, freezes killed entire mangrove forests dominated by black mangroves, Avicennia germinans (L.). Following the freezes, saltmarshes dominated by smooth cordgrass, Spartina alterniflora Loisel, revegetated the intertidal zone. After a decade of mild winters, however, mangroves are beginning to reclaim the area. The rate of mangrove expansion was determined by comparing aerial photography (change from 1995 to 1999), and from monitoring transects (over a 3 year period) on three of the Cedar Keys, Florida (Lat. 29°08′). The rate of mangrove expansion varied among islands, and the mechanism of expansion ranged from propagule-trapping by saltmarshes along the edges of mangrove clumps to widespread dispersal and growth of existing or newly imported propagules. A freeze occurred during the study, which may have set back mangrove expansion by defoliating mangrove trees and resetting mangrove reproduction. Mangrove expansion was projected to take 20–30 years for complete seedling cover. Given the possibility of global climate change and its potential influence on the distribution of coastal vegetation, the timeframes and implications to coastal wetland ecosystems involved in this regular interplay will provide valuable baseline information for future studies.     

Effect of an integrated mangrove-aquaculture system on aquacultural health

Mangroves are unique intertidal halophyte formations growing in sheltered tropical and subtropical coastal areas. Due to the increasing population and economic development, mangroves have faced degradation and loss, which has been mainly caused by land conversion into aquaculture ponds in Asia. In the past several decades, the rapid growth of aquaculture has induced water pollution. Using mangroves for effluent treatment from coastal aquaculture ponds could be a suitable approach for wastewater treatment and healthy aquaculture development. An Integrated Mangrove-Aquaculture System (IMAS) was established to test whether the idea of a mangrove in situ treatment for aquaculture wastewater is feasible. The monocultures of three mangroves, Sonneratia caseolaris, Kandelia obovata, and Aegiceras corniculatum were established with area proportions of 45%, 30%, or 15%, respectively. One control pond without mangroves was also set up. The results indicated that the mangroves had different tolerabilities to long-term inundation. The aquaculture ponds had different fishery yields, considering the mangrove species and area proportions. The water quality of most of the experimental ponds was better than the control pond, except for the planted Sonneratia. It is concluded that mangroves can reduce the concentration of dissolved inorganic nitrogen and phosphate, buffer the pH value and increase the concertration of dissolved oxygen in aquaculture water bodies effectively. It is suggested to use 15% of the Aegiceras corniculatum area to conduct in situ purification of aquaculture wastewater and to enhance aquaculture production.     

红树林恢复初期莱氏锥滨螺分布动态

树栖腹足类动物是红树林底栖动物的重要组成部分,其组成和分布受到红树植被的影响。因此,在红树林生态修复中,腹足类动物的恢复依赖于植被的发育。滨螺科(Littorinidae)锥滨螺属(Mainwaringia)动物是亚洲红树林的广布种,但针对其在红树林中的分布及种群特征的研究较少,对红树林植被恢复过程中锥滨螺属动物的恢复动态更是鲜有研究。调查了厦门下潭尾湿地秋茄(Kandelia obovata)红树林恢复初期,新记录种莱氏锥滨螺(Mainwaringia leithii)种群恢复的时间动态,并分析其与植被参数的关系。研究发现,红树林恢复初期,秋茄植被生长迅速,株高、冠幅、基径和覆盖度分别由0.5年生幼林的41.3 cm、25.0 cm、1.04 cm和25%增长为8年生样地的179.2 cm、76.7 cm、5.96 cm和95%。在秋茄胚轴种植6个月左右开始记录到莱氏锥滨螺的个体,其密度和生物量在1.5 a后达到最大(分别为136个/m²和1.86 g/m²),而后逐渐降低,种植3 a后秋茄林内莱氏锥滨螺仅零星分布。除8年生的样地,莱氏锥滨...     

Mangroves and brackishwater pond culture in the Philippines

Around 50% of mangrove loss in the Philippines can be traced to brackishwater pond construction. The decrease in mangroves from 450 000 ha in 1920 to 132 500 ha in 1990 has been accompanied by expansion of culture ponds to 223 000 ha in 1990. The history of fishpond development in the country includes a government-sponsored fishpond boom in the 1950-g and 1960s, the proconservation decade of the 1970s followed by a shrimp fever in the 1980s. Production from brackisshwater ponds has increased from 15 900 mt worth P7.6 million in 1938 to 267 000 mt valued at P6.5 billion in 1990. On the other hand, the maximum valuation of over $11 000 ha^–1 yr^–1 for unmanaged and managed mangrove forests makes them economically on par with the most profitable pond farming systems. The loss of mangrove systems and their varied goods and services is the single most important consequence of brackishwater pond culture in the Philippines. Moreover, intensive shrimp farming is associated with other ecological and socioeconomic effects such as pollution of coastal waters and decline in domestic food crops. New legislation and enforcement of existing laws, conservation of remaining mangroves, massive rehabilitation of denuded mangrove areas, and promotion of sustainable aquaculture and fisheries are recommended.     

Mariculture development in Kenya: alternatives to siting ponds in the mangrove ecosystem

Pond culture of brackishwater prawns and shrimps has recently generated much interest in Kenya. The mangrove areas are the target zones for the construction of these ponds. With the increasing awareness of the unique ecological role played by the mangroves, there is an urgent need to stop the conversion of mangrove swamps into aquaculture ponds. To develop pond aquaculture without destroying the mangroves, a shift from tide-fed to pump-fed pond systems is recommended in order to divert the farming from the mangroves to higher grounds. Mangrove-friendly mariculture practices like pen, cage and raft culture are discussed. Methods of efficiently utilising the already destroyed mangrove areas are considered.     

The role of saltwort (Batis maritima L.) in regeneration of degraded mangrove forests

While saltwort (Batis maritima L.) is common in the fringe mangrove forests of southwest Florida, its role in regeneration of degraded mangrove communities is not known. Given the potential encroachment and subsequent degradation of mangrove communities by sea-level rise, it is important to quantify the effect of early-colonizing vegetation to early mangrove seedling survival. A greater number of mangrove seedlings were observed in existing B. maritima patches compared to surrounding mudflats. A planting experiment was designed to determine whether B. maritima was responsible for the observed pattern. Black mangrove (Avicennia germinans L.) seedlings, raised in a nursery, were planted in previously established B. maritima patches and on mudflats with and without nursery-raised B. maritima. There was significantly lower mortality of A. germinans seedlings when planted in existing B. maritima patches (69%), compared to seedlings planted on the mudflats (93%), demonstrating that existing B. maritima improved A. germinans seedling survival. Nursery-raised B. maritima had lower mortality on open mudflats (28%), suggesting that it can tolerate conditions, which make it an early colonizer of newly available habitats. The primary mechanism proposed for improving seedling success is a slight increase in elevation provided by the dense root network of established B. maritima. These findings have implications for scientists and managers anticipating the response of mangroves to sea-level rise.     

Mangrove rehabilitation dynamics and soil organic carbon changes as a result of full hydraulic restoration and re-grading of a previously intensively managed shrimp pond

Hydraulic restoration by opening the shrimp pond banks facilitated the establishment of planted mangroves and colonisation by non-planted mangrove species and was shown to be an effective method of mangrove rehabilitation. Planted Rhizophora apiculata and Rhizophora mucronata had grown significantly in 6 years, to 300 and 350 cm, respectively. However, the growth rate of Bruguiera cylindrica was merely 150 cm in the same period despite vigorous growth in the initial stage. About 15 non-planted mangrove species had colonised within 6 years after reopening the banks, with the dominant species being Avicennia marina (46.9%) followed by B. cylindrica (27.0%) and Ceriops tagal (14.9%). After the enhancement, soil organic carbon increased considerably from 110 to 160 tonC ha⁻¹ in 2 years at the lower elevation, indicating that hydraulic restoration could stimulate carbon recovery through enhancement of mangrove growth. However, soil organic carbon decreased by almost half in the higher ground, suggesting that carbon decomposition was accelerated due to drying of soils.     

A newHalophytophthora species,H. porrigovesica, from subtropical and tropical mangroves

A new oomycete was found from intertidal fallen leaves of mangroves in Japan and Thailand and is described here asHalophytophthora porrigovesica. This species is characterized by having an epapillate, ovate zoosporangium with a lens-shaped dehiscence plug-like material at the apex, and by forming an expanding long cylindrical vesicle prior to zoospore release. A key to 14 species and 2 varieties ofHalophytophthora including the new species is proposed. The subtropical (Iriomote is., Japan) strains and tropical (Thailand) strains were different in physiological properties and especially in the asexual reproduction. The subtropical strains showed a lower optimal temperature and wider range of suitable temperature and salinity for zoosporangium formation, whereas the tropical strains showed a higher optimal temperature and narrower range of temperature and salinity. These differences are explained as adaptations of the strains to the environmental conditions of their respective habitats. From the subtropical mangroves, six strains of the new species have been isolated only from submerged leaves ofSonneratia alba, while several strains have been isolated from tropical mangroves from the leaves of three species of mangrove trees,S. alba, Bruguiera gymnorrhiza andAvicennia alba. This indicates a change of taxon selectivity (host specificity) with the geographical distribution.     

Nutrient and salt relations of <Emphasis Type="Italic">Pterocarpus officinalis</Emphasis> L. in coastal wetlands of the Caribbean: assessment through leaf and soil analyses

Pterocarpus officinalis L. is a dominant tree of freshwater coastal wetlands in the Caribbean and the Guiana regions. It is frequently associated with mangroves in areas with high rainfall and/or surface run-off. We hypothesized that P. officinalis is a freshwater swamp species that when occurring in association with mangroves occupies low-salinity soil microsites, or alternatively that it possesses mechanisms preventing accumulation of salt in photosynthetic tissues. To test this we compared the mineral composition of soils and leaves of several species in two Pterocarpus forests in Puerto Rico associated with coastal mangroves, Sabana Seca and Punta Viento. Results indicate that (1) Sabana Seca has low soil salinity values even in the P. officinalis and Laguncularia racemosa mixed zone. In Punta Viento, salinity in the mixed zone was higher than in the Pterocarpus forest, but much lower than in the mangrove area; (2) In both forests, leaves of P. officinalis showed much lower Na concentrations than mangrove species. The K/Na ratios were 16–20 times higher in P. officinalis, indicating preferential absorption of K against Na. The mangrove fern (Acrostichum aureum) growing side by side with P. officinalis and L. racemosa in Punta Viento also revealed high Na exclusion capacity. We found an asymmetric distribution of cations in the blade and rachis of the P. officinalis compound leaves in both sites. The rachis accumulates more Na and Ca, but less Mg than the leaf blade. This sequestration of Na in the rachis prevents salt damage of photosynthetic tissue in the leaf blade.     

Effect of an integrated mangrove-aquaculture system on aquacultural health

Mangroves are unique intertidal halophyte formations growing in sheltered tropical and subtropical coastal areas. Due to the increasing population and economic development, mangroves have faced degrada-tion and loss, which has been mainly caused by land conversion into aquaculture ponds in Asia. In the past several decades, the rapid growth of aquaculture has induced water pollution. Using mangroves for effluent treatment from coastal aquaculture ponds could be a suitable approach for wastewater treatment and healthy aquaculture development. An Integrated Mangrove-Aquaculture System (IMAS) was established to test whether the idea of a mangrove in situ treatment for aquaculture wastewater is feasible. The monocultures of three mangroves, Sonneratia caseolaris, Kandelia obo-vata, and Aegiceras corniculatum were established with area proportions of 45%, 30%, or 15%, respectively. One control pond without mangroves was also set up. The results indicated that the mangroves had different toler-abilities to long-term inundation. The aquaculture ponds had different fishery yields, considering the mangrove species and area proportions. The water quality of most of the experimental ponds was better than the control pond, except for the planted Sonneratia. It is concluded that mangroves can reduce the concentration of dissolved inorganic nitrogen and phosphate, buffer the pH value and increase the concertration of dissolved oxygen in aqua-culture water bodies effectively. It is suggested to use 15% of the Aegiceras corniculatum area to conduct in situ purification of aquaculture wastewater and to enhance aquaculture production.