Trapping of Rhizophora mangle Propagules by Coexisting Early Successional Species

Distributions of mangroves in coastal wetlands are influenced by abiotic conditions and the net effect of biotic interactions, including competition, facilitation, and consumer pressure. In coastal wetlands, early successional shrubs, herbs, and grasses may facilitate recruitment of mangroves through multiple mechanisms, including amelioration of environmental conditions, propagule trapping, and structural support. In Mosquito Lagoon, FL, we observed an aggregated distribution of Rhizophora mangle propagules along vegetated shorelines with Batis maritima and Sarcocornia perennis and hypothesized that this distribution was a result of propagule trapping by the vegetation. We designed a field experiment to evaluate retention of R. mangle propagules on vegetated and unvegetated shorelines in Mosquito Lagoon. Significant differences were found in the retention time of mangrove propagules at each shoreline type, with vegetated shorelines retaining propagules significantly longer than unvegetated shorelines. Results from this study help to define facilitative mechanisms which may be important in successional processes of coastal wetlands and have direct restoration applications. Successful recovery of mangroves at restoration sites may be facilitated by establishment of B. maritima and S. perennis, when natural propagule sources are available, or through planting mangrove seedlings into existing stands of these halophytes when restoration areas are propagule-limited.     

The role of large rhizome dispersal and low salinity windows in the establishment of common reed,<Emphasis Type="Italic">Phragmites australis</Emphasis>, in salt marshes: New links to human activities

In spite of its long history,Phragmites australis’ (Cav.) Trin ex Stuedel invasion in tidal marshes defies explanation. Initial establishment in these systems is particularly perplexing, because seedlings and rhizome fragments do not perform well in poorly drained saline environments. We tested the possibility that dispersal and burial of large rhizomes, periods of low salinity, and localized, well-drained areas facilitate initial establishment in brackish marshes. In a greenhouse we exposed large and small rhizomes to two drainage treatments: mimics of poorly-drained, high marsh interiors and mimics of well-drained, mosquito ditch banks. In well-drained treatments we exposed rhizomes to one of three salinity treatments: fresh, natural salinity regime of an invaded brackish water marsh, and a 2-wk freshwater window followed by a natural salinity regime. Small rhizone fragments did not emerge in saline treatments or treatments with high water tables, while emergence was spotty in well-drained freshwater treatments. Large rhizomes emerged only in well-drained, treatments. For large rhizomes, growth, survival, and clonal spread decreased when exposed to the natural salinity regime, but improved with exposure to the 2-wk freshwater window. These results suggest that dispersal and burial of larger rhizomes, well-drained features, and low salinity windows following dispersal improve the chances of successful establishment. These results help explain case-specific historical links between establishment and such human activities as hydrological alterations, construction activities, and lowered salinity.     

Temperature Tolerance of Early Life History Stages of Black Mangrove <Emphasis Type="Italic">Avicennia germinans</Emphasis>: Implications for Range Expansion

Avicennia germinans (L.) L. (black mangrove) grows at its North American latitudinal limit in coastal salt marshes of Louisiana, USA. To assess low-temperature tolerance of A. germinans, we evaluated the survival and developmental progress of three early life history stages (dispersal, stranded, and seedling stages) to three temperatures (5.7°C, 2.5°C, and −6.5°C) of four durations (2, 6, 12, and 24 h). Duration and temperature of exposure decreased mangrove survivorship, particularly 24-h exposure at −6.5°C. Although there was not a significant effect of stage on survivorship overall, both survival analysis and final mortality analysis indicate that dispersal stage had the greatest survivorship. Treatments had little impact on developmental progress of surviving propagules, but propagules exposed to −6.5°C were most susceptible to fungal infection. Greater cold temperature tolerance of the dispersal stage may be a mechanism for northward range expansion in Louisiana.     

Stand-level dieback etiology and its consequences in the forests of Papua New Guinea

Stand-level dieback inNothofagus, mangrove andEucalyptus deglupta forests is examined. InNothofagus and mangrove forests, groups of largely even-aged trees die simultaneously, possibly triggered by drought stress which may directly affect the trees inNothofagus forests or indirectly increase water salinity in mangroves. Lightning strikes may be an additional dieback trigger in mangroves. Crown decline only was observed inE. deglupta forests and this may be associated with water-logging during periods of exceptionally high rainfall. Examination of rainfall records shows that severe droughts occur periodically in association with El Nino Southern Oscillations in the Pacific Ocean.     

Impact and response of southwest Florida mangroves to the 2004 hurricane season

Although hurricane disturbance is a natural occurrence in mangrove forests, the effect of widespread human alterations on the resiliency of estuarine habitats is unknown. The resiliency of mangrove forests in southwest Florida to the 2004 hurricane season was evaluated by determining the immediate response of mangroves to a catastrophic hurricane in areas with restricted and unrestricted tidal connections. The landfall of Hurricane Charley, a category 4 storm, left pronounced disturbances to mangrove forests on southwest Florida barrier islands. A significant and negative relationship between canopy loss and distance from the eyewall was observed. While a species-specific response to the hurricane was expected, no significant differences were found among species in the size of severely impacted trees. In the region farthest from the eyewall, increases in canopy density indicated that refoliation and recovery occurred relatively quickly. There were no increases or decreases in canopy density in regions closer to the eyewall where there were complete losses of crown structures. In pre-hurricane surveys, plots located in areas of management concern (i.e., restricted connection) had significantly lower stem diameter at breast height and higher stem densities than plots with unrestricted connection. These differences partially dictated the severity of effect from the hurricane. There were also significantly lower red mangrove (Rhizophora mangle) seedling densities in plots with restricted connections. These observations suggest that delays in forest recovery are possible in severely impacted areas if either the delivery of propagules or the production of seedlings is reduced by habitat fragmentation.     

Vegetation change in the coastal-lowland rainforest at Avai'o'vuna Swamp, Vava'u, Kingdom of Tonga

Avai'o'vuna Swamp, a small coastal wetland in Vava'u, Kingdom of Tonga, produced a 4500-year pollen and sediment record. Results are: (1) a mid-Holocene sea level highstand is confirmed for Tonga between about 4500 and 2600 ¹⁴C yr B.P.; marine clay contains pollen from mangroves (Rhizophora mangle), coastal forest trees (Barringtonia asiatica and Cocos nucifera), and rainforest trees (Alphitonia, Rhus, Hedycarya and Calophyllum). (2) Microscopic charcoal first appeared at 2600 ¹⁴C yr B.P., coincident with the arrival of Polynesians. (3) Cocos, Pandanus, Excoecaria, Macaranga, and Elaeocarpaceae pollen reflects the establishment of a mixed coastal-lowland rainforest in the last 2500 years. (4) The loss of Hedycarya, Elaeocarpus, Calophyllum, and Guettarda and the reduction of Terminalia and taxa in the Papilionaceae family by about 1000 years ago may be due to habitat destruction and the loss of dispersal capabilities of some species through the extinction of the two largest pigeons in Tonga.     

Analysis and Simulation of Propagule Dispersal and Salinity Intrusion from Storm Surge on the Movement of a Marsh–Mangrove Ecotone in South Florida

Coastal mangrove–freshwater marsh ecotones of the Everglades represent transitions between marine salt-tolerant halophytic and freshwater salt-intolerant glycophytic communities. It is hypothesized here that a self-reinforcing feedback, termed a “vegetation switch,” between vegetation and soil salinity, helps maintain the sharp mangrove–marsh ecotone. A general theoretical implication of the switch mechanism is that the ecotone will be stable to small disturbances but vulnerable to rapid regime shifts from large disturbances, such as storm surges, which could cause large spatial displacements of the ecotone. We develop a simulation model to describe the vegetation switch mechanism. The model couples vegetation dynamics and hydrologic processes. The key factors in the model are the amount of salt-water intrusion into the freshwater wetland and the passive transport of mangrove (e.g., Rhizophora mangle) viviparous seeds or propagules. Results from the model simulations indicate that a regime shift from freshwater marsh to mangroves is sensitive to the duration of soil salinization through storm surge overwash and to the density of mangrove propagules or seedlings transported into the marsh. We parameterized our model with empirical hydrologic data collected from the period 2000–2010 at one mangrove–marsh ecotone location in southwestern Florida to forecast possible long-term effects of Hurricane Wilma (24 October 2005). The model indicated that the effects of that storm surge were too weak to trigger a regime shift at the sites we studied, 50 km south of the Hurricane Wilma eyewall, but simulations with more severe artificial disturbances were capable of causing substantial regime shifts.     

Mangrove zonation in the dry life zone of the Gulf of Fonseca, Honduras

The structural attributes and zonation patterns of mangrove forests in a dry environmental setting were evaluated in relation to gradients of soil resources, soil regulators, and hydroperiod between October 2000 and August 2001 in the Gulf of Fonseca, Honduras. Transects perpendicular to the edge of tidal channels were established at four mangrove sites, each sectioned into three mangrove zones (fringe, transition, and scrub) based upon distinct tree-height gradients. Porewater sulfide concentrations among zones were normally below levels of detection (<0.03 mM) and mean redox values ranged from 163.4±9.9 to −42.4±15.8 mv, indicating slightly reducing conditions in all zones. Mean porewater NO_x ⁻ and PO₄ ³⁻ concentrations were not significantly different among zones and ranged from 3.3±0.5 to 4.5±0.4 μM and from 0.05 ±0.02 to 0.18±0.04 μM, respectively. Soil nitrogen concentrations were 1–3 mg g⁻¹ in all zones, and mean nitrogen:phosphorus atomic ratios were <20 (range: 12.9–14.9), indicative of fertile wetland soils. Mean basal areas were significantly different among mangrove zones (fringe > transition) and were coupled with differences in height within species and zones.Avicennia germinans occupied areas with higher elevations associated with higher salinities ranging from 80 to 140 g kg⁻¹ in the dry season.Rhizophora mangle dominated lower elevations where salinities ranged from 38 to 57 g kg⁻¹ in both the dry and wet seasons. Spatial analysis on mangrove seedlings along transects confirmed that seedling distribution along the intertidal profile was statistically correlated with conspecific adults, indicating that survival and growth of seedlings in different intertidal locations are closely matched to canopy membership. The sharp transition (<100 m) in forest structure and distribution of mangrove species along the intertidal zone of subhumid coastal environments demonstrate common zonation patterns where species distribution and species-specific habitat suitability are mediated closely with tolerance to soil regulators (high soil salinity) rather than resource availability.     

Effects of two hurricanes onSyringodium filiforme, manatee grass, within the Loxahatchee River estuary, Southeast Florida

In September 2004, the Loxahatchee River Estuary was affected by Hurricanes Frances and Jeanne, which resulted in a monthly rainfall record of 610 mm and abnormally high freshwater discharges to the system. The occurrence, density, and biomass ofSyringodium filiforme in the Loxahatchee River Estuary declined significantly following the September 2004 storms based on 15 mo of pre-hurricane monitoring and 12 mo of post-hurricane monitoring. Throughout posthurricane monitoring,S. filiforme showed no sign of recovery, thoughHalophila johnsonii increased considerably during the post-hurricane period. Freshwater discharges resulting from the September 2004 hurricanes lowered minimum daily salinity values to near zero and increased standard deviation of daily salinity values to 11‰. Extremely low minimum daily salinity values and high daily salinity fluctuations likely resulted in the observed decline ofS. filiforme. We advise the use of minimum daily salinity values when assessing seagrass habitat suitability or when modeling the effects of alternative water management scenarios.     

Coupling near-surface geomorphology with mangrove community diversity at the estuarine scale: A case study at Dongzhaigang Bay,China

Coastal wetlands are key features of the Earth's surface and are characterized by a diverse array of coupled geomorphological and biological processes. However, the links between the distribution of biodiversity (for example, species and structural diversity) and the formation of coastal geomorphology are not well-understood on a landscape scale most useful to coastal zone managers. This study describes the relationship between select geomorphological and biological mangrove community features (i.e. species composition and functional root type) in a landscape-distributed coastal zone of Dongzhaigang Bay, north-eastern Hainan Island, China. A total of 11 mangrove species and five functional aerial root types were encountered, with the location of species by root types being controlled by the elevation of the soil surface. Plank roots, prop roots and pneumatophores occupied the lowest intertidal elevations, while knee roots and fibrous roots of the mangrove fern, Acrostichum aureum, preferred the highest intertidal elevations. Surface sediment deposition in areas with mangroves was greater than deposition in non-mangrove forest zones, establishing an important biological mechanism for this large-area response because surface erosion/compaction was also more prominent within mangrove roots. Indeed, functional root type influenced the magnitude of deposition, erosion and compaction, with knee roots and pneumatophores being more effective in promoting deposition and preventing surface erosion/compaction than prop roots. These results indicate a potential role for vegetation type (especially functional root type) to influence coastal geomorphological processes at large landscape scales. While soil surface elevation is correlated to the distribution of mangrove species and functional root types, a significant feedback exists between elevation change and the capacity of those root types to influence coastal geomorphological differentiation within sustainable intertidal elevations. An enhanced understanding of geomorphological development, mangrove species distribution and functional root type may improve management to support nature-based solutions that adjust more effectively to sea-level rise through feedbacks.     

全球气候变化对红树林生态系统的影响与研究对策

红树林生态系统出现于热带和亚热带的潮间带，是一个脆弱或敏感的生态系统，受到陆相和海相的双重影响，可能是全球气候变化影响的早期指示者。气候变化引起海平面升高的速率在９－１２ｃｍ／１００ａ时或超过红树林底质的沉积速率时，红树林就受到胁迫甚至消亡。平均气温上升可能造成红树林种类组成的变化。一定限度的升温有利红树植物的生长发育，但太高温度不利其叶的形成和光合作用，温度的累积作用会有相当大的影响，并通过土壤     

Investigations of the availability and survival of submersed aquatic vegetation propagules in the tidal Potomac River

The establishment of submersed aquatic vegetation (SAV) at unvegetated sites in the freshwater tidal Potomac River was limited primarily by factors other than propagule availability. For two years, traps were used to quantify the amount of plant material reaching three unvegetated sites over the growing season. The calculated flux values provided a gross estimate of the flux of propagules that could potentially survive if other site factors were suitable. The mean flux ofHydrilla verticillata and all other species (≥0.01 gdw m^?2 d^?1) appeared sufficient to favor the establishment of vegetation, particularly considering the high viability (70–100%) of whole plants and fragments under controlled conditions. However, median water clarity values (i.e., for light attenuation, Secchi depth, total suspended solids, and chlorophylla) were below SAV restoration goals at all unvegetated sites. Additionally, sediments from unvegetated sites showed a potential for nitrogen limitation of the growth ofH. verticillata. Our findings support the hypothesis that in the tidal Potomac River, water clarity and nutrient (especially nitrogen) levels in sediment are key to plant community establishment.     

Food and habitat partitioning in grazing snails (<Emphasis Type="Italic">Turbo smaragdus</Emphasis>), Northern New Zealand

Gut content analyses and fatty acid profiles were used to identity food consumption and assimilation in a dominant grazing snail (Turbo smaragdus) in rocky shore and estuarine habitats, at Waiwera Estuary, northern New Zealand. Gut contents of freshly collected individuals indicated that snails utilize a wide range of food sources within their habitats, including microalgae and foliose-corticated macrophytes (rocky intertidal), and mangrove tissue and filamentous algae (mangrove stand). Laboratory feeding experiments revealed thatT. smaragdus prefers microalgae and possibly filamentous epiphytes, regardless of snail size or habitat of origination. The fatty acid profiles of snails fed different diets (brown algae [Hormosira banksii], diatoms, mangrove pneumatophores, and filamentous green algae [Chaetomorpha sp.]) confirmed the assimilation of the given foods, except for the mangrove treatment, which resulted in a low, long chain, fatty acid (LCFA) signature. Incongruities between the gut content analyses (high number of mangrove particles) and fatty acid profiles (low LCFA signature) of field and laboratory snails exposed to a mangrove diet suggest that snails target microalgal and filamentous epiphyte food sources on the pneumatophores and inadvertently ingest mangrove particles. Snails within all food treatments, except diatoms, had a relatively strong bacterial signature (18∶1n–7, Σ15+Σ17). Bacteria may have readily accumulated in the experimental tanks and been selected by snails as an alternative food source. In the field, snails and other grazers may ingest detritus and biofilms to access dense populations of bacteria. This research highlights the need for a comprehensive and multianalytical approach to elucidate the role of grazers in algal-plant dominated ecosystems.     

<Emphasis Type="Italic">Phragmites australis</Emphasis> invasion and expansion in tidal wetlands: Interactions among salinity,sulfide, and hydrology

Through their physiological effects on ion, oxygen, and carbon balance, respectively, salinity, sulfide, and prolonged flooding combine to constrain the invasion and spread ofPhragmites in tidal wetlands. Initial sites of vigorous invasion by seed germination and growth from rhizome fragments appear limited to sections of marsh where salinity is <10‰, sulfide concentrations are less than 0.1 mM, and flooding frequency is less than 10%. In polyhaline tidal wetlands the invasion sites include the upland fringe and some high marsh creek banks. The zones of potential invasion tend to be larger in marshes occupying lower-salinity portions of estuaries and in marshes that have been altered hydrologically. Owing to clonal integration and a positive feedback loop of growth-induced modification of edaphic soil conditions, however, a greater total area of wetland is susceptible toPhragmites expansion away from sites of establishment. Mature clones have been reported growing in different marshes with salinity up to 45‰, sulfide concentration up to 1.75 mM, and flooding frequency up to 100%. ForPhragmites establishment and expansion in tidal marshes, windows of opportunity open with microtopographic enhancement of subsurface drainage patterns, marsh-wide depression of flooding and salinity regimes, and variation in sea level driven by global warming and lunar nodal cycles. To avoidPhragmites monocultures, tidal wetland creation, restoration, and management must be considered within the context of these different scales of plant-environment interaction.     

Structure and dynamics of mangrove forests along a flooding gradient

The zonation patterns ofAvicennia bicolor andRhizophora racemosa were studied in a mangrove forest on the Pacific Coast of Costa Rica. Comparisons were made between the establishment, survival, and growth of both species in three plots, 1 ha each, located along the flooding gradient. Based on cohort analysis and reciprocal planting observations, it was concluded that species zonation was primarily regulated by the depth of tidal inundation and the differential ability of the propagules to become established. However, tidal sorting was not the only operative factor related to inundation. Drought and probably high soil salinities limited the survival and growth ofR. racemosa in the landward sections of the forest. Tidal sorting, however, confined propagules to zones where they probably had the highest likelihood of contributing to another generation.     

Red Mangrove Seedling Survival, Growth, and Reproduction: Effects of Environment and Maternal Genotype

An adequate understanding of the nature and extent of response to stressors and resources by marine foundation plant species requires study of local adaptation and plasticity in traits. Analyses of variation among genotypes in growth and morphology and genotype × environment interactions are necessary for restoration in, for example, different combinations of tide, soil, and salinity regimes, and for assessing how foundation plant species will respond to global climate change. We conducted a field experiment to assess differences in responses among 86 half-sibling (same maternal tree) seedling families of the red mangrove (Rhizophora mangle) to different environmental conditions of hydrology imposed at low- and high-intertidal settings. At 3 years, Rhizophora survival and growth varied with maternal tree genotype, elevation, and genotype × elevation. This effect was independent of size of propagules at planting. Growth also differed among the five islands planted, a main effect that is a composite of a number of microenvironmental differences stemming from island size and shape, proximity to passes (and thus fetch), and island slope. Significant genotype × island interactions for some response variables further support the hypothesis that seedlings of different maternal genotypes can perform very differently under various suites of environmental conditions. Planted seedlings reproduced at an early age, and at 3 years there were differences in reproductive output among genotypes but not an overall mean difference between plants at low or high elevation. Whether our results show adaptation to local conditions or differences in plasticity among genotypes will require further study as the plants mature further to demonstrate fitness differences. However, either adaptation or plasticity provides a basis for maintenance of Rhizophora dominance over a wider range of environmental conditions and may be important for adaptation to conditions that will vary with global climate change.     

Red mangrove (Rhizophora mangle) reproduction and seedling colonization after hurricane charley: Comparisons of Charlotte Harbor and Tampa Bay

Reproductive aspects of life history are known to be important in recovery following disturbance in many plant species although this has not been well studied in mangroves. Hurricane Charley devastated large areas of mangroves in Charlotte Harbor, Florida, in August 2004. We surveyed 6 forests in Charlotte Harbor (2002, 2003, and 2005) and 16 in Tampa Bay, Florida (2001, 2002, 2003, and 2005) for total numbers of reproducing trees and trees heterozygotic for albinism that produce both normal and albino propagules. Tree size (estimated height and diameter at breast height) was also recorded for sentinel heterozygotic trees. Total number of reproducing trees km⁻¹ was used as an index of reproductive output of the population, and deviation from the 3∶1 (normal:albino propagules) ratio on heterozygotic trees expected with 100% selfing was used to estimate outcrossing. Numbers ofRhizophora mangle reproducing trees km⁻¹ of shoreline in Charlotte Harbor were reduced by an order of magnitude following Hurricane Charley, while numbers of reproducing trees in Tampa Bay were similar to those of previous years. Reduced reproduction in Charlotte Harbor was accompanied by fewer new recruits in plots on Sanibel and Captiva Islands. Numbers of new recruits after the storm also tended to be fewer in plots where canopy loss was greater. More new recruits occurred in sites that had higher densities of pre-stormRhizophora seedlings and greater relative dominance byRhizophora. Outcrossing of sentinel trees was 2.5 times greater, in Charlotte Harbor (mean site⁻¹=33.6±6.7%; with 17% of forest sites completely selfing) than in Tampa Bay (mean site⁻¹=13.4±4.7%; with 40% of sites completely selfing), although the implications for seedling recruitment of this difference are not known.     

Progradational Holocene carbonate tidal flats of Crooked Island,south‐east Bahamas: An alternative to the humid channelled belt model

The stratigraphic record of many cratonic carbonate sequences includes thick successions of stacked peritidal deposits. Representing accumulation at or near sea‐level, these deposits have provided insights into past palaeoenvironments, sea‐level and climate change. To expand understanding of carbonate peritidal systems, this study describes the geomorphology, sedimentology and stratigraphy of the tidal flats on the Crooked‐Acklins Platform, south‐east Bahamas. The Crooked Island tidal flats extend continuously for ca 18 km on the platformward flank of Crooked Island, reaching up to 2 km across. Tidal flats include four environmental zones with specific faunal and floral associations and depositional characteristics: (i) supratidal (continuous supratidal crust and pavement); (ii) upper intertidal, with the mangrove Avicennia germinans and the cyanobacteria Scytonema; (iii) lower intertidal (with the mangrove Rhizophora mangal) and (iv) non‐vegetated, heavily burrowed subtidal (submarine). These zones have gradational boundaries but follow shore‐parallel belts. Coring reveals that the thickness of this mud‐dominated sediment package generally is <2 m, with depth to Pleistocene bedrock gradually shallowing landward. The facies succession under much of the tidal flat includes a basal compacted, organic‐rich skeletal‐lithoclast lag above the bedrock contact (suggesting initial flooding). This unit grades upward into rhizoturbated skeletal sandy mud (subtidal) overlain by coarsening‐upward peloid‐foraminifera‐gastropod muddy sand (reflecting shallowing to intertidal elevations). Cores from landward positions include stacked thin indurated layers with autoclastic breccia, root tubules and fenestrae (interpreted as supratidal conditions). Collectively, the data reveal an offlapping pattern on this prograding low‐energy shoreline, and these Holocene tidal flats may represent an actualistic analogue for ancient humid progradational tidal flats. Nonetheless, their vertical facies succession is akin to that present beneath channelled belt examples, suggesting that facies successions alone may not provide unambiguous criteria for prediction of the palaeogeomorphology, lateral facies changes and heterogeneity in stratigraphic analogues.     

The history of the mangrove vegetation in Bénin during the Holocene: A palynological study

Pollen analysis of three core samples,YEV-I, GOHO.00 and DO.00, taken in the coastal area of Bénin shows the existence of mangrove during the Holocene. This mangrove underwent many physiognomic changes from the middle to the late Holocene. In the course of the middle Holocene (from 7500 to 2500 years before present (BP)), it stretched over a large area from the littoral inland. It was tightly closed and almost monospecific, dominated by Rhizophora. During the late Holocene, this mangrove started to regress around 3000 years BP and disappeared about 2500 years BP from the studied sites. It has been replaced by swamp meadows dominated by Paspalum vaginatum Sw. and a fresh water environment colonised by taxa such as Persicaria, Typha, Ludwigia, and Nymphaea.     

Spatial and temporal variations of meiofaunal communities from the Western Sector of the Gulf of Batabanó, Cuba. I. Mangrove systems

The spatial and temporal variations of meiofaunal communities in mangrove systems were examined. Replicated cores were taken in mudflats between prop roots ofRhizophora mangle at five locations within the Gulf of Batabanó, Cuba, during 3 mo. There was a clear seasonality in the water column, but measured abiotic variables did not show obvious relations with meiofaunal patterns. The magnitude of change in salinity for each location appears to influence the meiofauna more than absolute values per se. The meiofauna from southern Pinar del Rio showed a higher variation in community structure, suggesting higher levels of stress in comparison with locations in eastern Isla, possibly due to the presence of human settlements, runoff from land, and apparent deterioration of mangroves. The considerable variation in the density and community structure estimates on global (geographical regions) and local (locations in the Gulf of Batabanó) scales could be caused by the high spatial variability in the mangrove microenvironment, coupled with associated methodological differences in the sampling. There was a low density of meiofauna (mean: 101 animals 10 cm⁻²) compared to other shallow tropical habitats. Mangroves from subtropical and temperate regions showed consistently higher meiofaunal densities than tropical mangroves, but causes of this putatively latitudinal pattern require further study. Future strategies for meiofaunal studies in mangrove systems should increase the temporal and spatial replication, include designed field experiments to test ecological hypotheses, and apply a species level approach with regards to nematode assemblages.