The results may provide valuable ecological information for environmental managers seeking to control the spread of mangroves in the estuaries of northern New Zealand. Seagrasses grow both vertically and horizontallytheir blades reach upwards and their roots down and sidewaysto capture sunlight and nutrients from the water and sediment. Florida’s fisheries would suffer a dramatic decline without access to healthy mangrove habitats. Litter production and decomposition in the New Zealand mangrove, Studies of a mangrove basin, Tuff Crater, New Zealand: I. Mangrove biomass and production of detritus, A spatial analysis of the relationship between mangrove (, © 2010 International Council for the Exploration of the Sea. It has been suggested that natural and anthropogenic changes to the structure of mangrove stands have a direct impact on the physical processes operating within the habitat and their associated fauna (Wolanski et al., 1992). Wetland - Wetland - Wetland functions and ecosystem benefits: Wetland functions are defined as the physical, chemical, and biological processes or attributes that are vital to the integrity of the wetland system. Note that there was no pneumatophore habitat at Site 2. Vascular plants have a strong influence on coastal community structure, function, and successional patterns (Bertness, 1991, 1992; Snelgrove et al., 2000; Bortolus et al., 2002; Levin and Talley, 2002). (2006) in Matapouri Estuary, northern New Zealand. Furthermore, the survival of juvenile fish is aided by the long residence time of water amongst the mangroves, which is facilitated by the mangrove roots. This then has negative economic consequences for regional economies that have substantial input from fish based industries. While these losses are felt most intensely by communities that have removed or degraded their mangroves, they ultimately affect all of us through reduced food security, enhanced migration, and increased … Mangrove swamps protect coastal areas from erosion, storm surge (especially during hurricanes), and tsunamis. On Bimini, a decline in survival of young lemon sharks has been correlated to developments on the island, causing a 23% decline in first-year survival of the young sharks 2. When mangroves are removed from an estuarine environment, many of these ecosystem services that aid the survival and production of fisheries can be either lost or diminished in value. For full access to this pdf, sign in to an existing account, or purchase an annual subscription. Today’s top headlines Sign up for the Afternoon Update and get the day’s biggest stories in your inbox. The most abundant organism, Potamopyrgus antipodarum, had an overall mean density (±s.e.) Special thanks are also due to the LaBonté's for their support with field logistics and scientific discussions. Technical annex. What are your alternative management strategies? Climate, landscape shape (topology), geology and the movement and abundance of water help to determine the plants and animals that inhabit each wetl… Component 2 was highly variable in its loading composition. In general, tropical rehabilitated areas have shown an increase in species abundance and biodiversity associated with mangrove plantations (Botero and Salzwedel, 1999; Sherman et al., 2000; Macintosh et al., 2002). Therefore, mangroves in subtropical and tropical regions are regarded as biologically important areas that provide food and shelter for a diversity of organisms and result in rich ecosystems (Laegdsgaard and Johnston, 2001; Valiela et al., 2001; Diop, 2003; Duke et al., 2007). They provide a habitat for a diverse array of terrestrial organisms and are the nesting sites for many species of birds. In western Kincumber Broadwater, New South Wales, Australia, dramatic changes in benthic faunal composition and increased community structure variability took place after mangrove canopy pruning (from 5 to 1 m height; Gladsone and Schreider, 2003). The ecological study was conducted between March 2004 and September 2006, with sampling once before and five times after the April 2004 mangrove tree-removal activities. Principal component analysis (PCA) was used to detect habitat differences, based on sediment characteristics for each sampling date. In Hawaii, where mangroves (R. mangle) also are spreading rapidly, a high propagule production rate (Cox and Allen, 1999) and a lack of propagule predators (Steel et al., 1999) have been suggested as two potential reasons for the success of mangroves there (Chimner et al., 2006). However, it is important to note that contrary to mangroves in Hawaii, Avicennia marina australasica is endemic to New Zealand and may require a different management system. Wetlands are among the most productive ecosystems in the world, comparable to rain forests and coral reefs. Multiple dimension scaling (MDS) plots were constructed, based on similarities of correlation matrices, to detect groupings of habitat type for each sampling date. Other sites have experienced little or no increase in mangrove area, mostly because of the small size of the estuary or elevation limits on their landward sides (Morrisey et al., 2007). This service is particularly important where the surrounding region contains seagrass or coral reefs given that these habitats are particularly vulnerable to deterioration if water quality declines3. That snail has been reported to live in the muddy substrata of mangrove habitats (May, 1999; Morrisey et al., 2002; Ellis et al., 2004). Its tolerance to muddy sediments is reflected by its extended distribution, in lesser numbers, into the mangrove habitats. The results also suggest that ecological changes may extend beyond the immediate area (∼100 m) and into other habitats and that the effects may persist for 3 or more years after the event. How do you combine these assessments to make decisions? of 0.04 ± 0.00 and 0.23 ± 0.01 m−3, respectively (Figure 8). For instance, it has been suggested that the comparatively smaller amounts of food produced by a diminished mangrove area will cause a decline in the rate of reproduction amongst mangrove dwelling fish to decline. Both habitats can be adversely impacted by oil spills, and spill responders must often consider tradeoffs between land-based and offshore resources during a response. Unfortunately many pages may not be where they used to be because this is such a major upgrade. Mangroves are extremely important ecologically. To date, there is insufficient scientific information to clearly evaluate the ecological importance of New Zealand's mangroves. The shallow water environment of the mangrove estuary area and the mangrove roots themselves protect these juvenile fish from predators like larger fish and birds1. However, studies often are limited by constrained experimental designs, low replication, and a lack of suitable controls. Each replicate sediment sample was sieved through a 2-cm and then a 0.5-mm mesh. In fact, Alfaro (2006) suggested that the low abundance of mangrove grazers (i.e. of total individuals and total taxa within different habitats at three sites (Site 1, mangrove-removal area; Sites 2 and 3, control sites) from March 2004 to September 2006 (mangrove removal illustrated by vertical dashed line). IUCN, Macrobenthic infauna of mangroves and surrounding beaches at Gazi Bay, Kenya. Faculty of Health and Environmental Sciences, School of Applied Sciences, Auckland University of Technology. A distinct separation of mangrove habitat at Site 1 (mangrove-removal site) was found at and after September 2004, which agrees with the increase in sand composition there immediately after mangrove removal (Figure 9). Without mangroves, “red tide” algae blooms in the water, kills sea life, and shuts down beaches. Mangroves also are seen as an unwanted species in Hawaii, where introduction of Rhizophora mangle in the early 1900s initiated a dramatic change in the native habitat of endangered Hawaiian waterbirds (Allen, 1998; Cox and Allen, 1999; Rauzon and Drigot, 2002). Mean abundance (±s.e.) What are phytoplankton, and what might happen to an aquatic food web is phytoplankton were removed from the ecosystem? Although all mangrove trees were removed from the site, the results from the September 2004 sampling event showed a greater number of pneumatophores within the mangrove and pneumatophore habitats, probably a consequence of the removal of the uppermost sediments by water motion, which could have uncovered shorter pneumatophores. But mangroves have had to adapt to all this mud. A keystone species, by definition, has the power to largely effect entire ecosystems simply by performing natural behaviors for survival. A slight increase followed by a decrease in population density over time for this species was apparent for Sites 1 and 2, probably a consequence of their normally patchy distribution around food sources, which vary in time and space. We asked if they had had any problems with their mangroves and would like them removed, if and how they used the area for recreation and what wildlife they had seen. Disturbed and undisturbed mangrove areas, adjacent pneumatophore zones, marshgrass, sandflats, and subtidal channels were monitored over time to test the hypotheses that (i) mangrove removal would alter sediment characteristics, (ii) mangrove removal would change the benthic faunal composition, and (iii) variations in sediment characteristics and faunal composition would differ among habitats (i.e. The snail Zeacumantus lutulentus was found in all habitats, with an overall density of 0.38 ± 0.00 m−3, but was most common in the pneumatophore, sandflat, and channel habitats (Figure 5). At Site 1, the organic content in all habitats, but especially in the mangroves and pneumatophores, increased slightly immediately after mangrove removal (Figure 11). “Trade-offs of mangrove area development in the Philippines”. seagrass beds, sandflats), which they argue has detrimental ecological and socio-economic effects (Green et al., 2003; Schwarz, 2003). Highly mobile species, such as the crab H. crassa, dramatically increased in abundance following mangrove removal at Site 1, then slowly decreased in subsequent sampling dates. In addition to its social and economic importance, the mangrove crab is a “keystone” specie in ecosystem, they playing an important role in the processes of nutrient cycling and … These differences may be related to mature trees tending to form dense mats of fibrous roots, which may not provide a suitable habitat for many macroinvertebrates. Where can you find guidelines for environmental values? Mangrove loss exemplifies how climate change not only causes destruction, but also perpetuates and intensifies itself. 1, The marine environment / edited by Leon P. Zann, Patricia Kailola. This intrinsic characteristic of older mangrove stands may make it difficult for benthic fauna to inhabit these areas, as suggested by Alfaro (2006). Mean abundance (±s.e.) Primarily this is because the fish will divert energy away from reproduction to competition for an ever-smaller reserve of food1. In the short term, there is considerable potential for these projects to result in positive economic gains. More recently, investigations on the role of associated flora and fauna within these habitats have increased in number (Morrisey et al., 2002; Alfaro, 2006; Alfaro et al., 2006). It is estimated that one-third of the world's mangrove forests have been lost in the past 50 years (Alongi, 2002). Mean abundance (±s.e.) The 0.26-ha area of mangrove removal is located on the east side of the causeway, just north of the bridge (Figure 1). This aggregation behaviour also may be responsible for its high densities in the marshgrass and mangrove habitats. If the mangrove didn’t have such a barrier, the salty ocean water would suck the mangrove dry. The temporal patterns in grain-size composition indicate that Site 1 experienced a general decrease in fine sand from March to September 2004, especially for the mangrove, pneumatophore, and sand habitats (but not the channel in Site 1), and an increase in finer sediments from September 2005 to September 2006 (Figure 9). Read all about Natural Resource Management including: Visit the Natural Resource Management page or browse through this menu to find information on specific topics. It would be a world without mangrove tigers, mangrove honeyeaters, mud crabs or mangrove mud whelks. Although the densities of both groups of worm varied over time, no dramatic temporal changes were observed at Sites 2 and 3 (except for some instances at Site 3), indicating their success within muddy/sandy habitats. The scope of water quality management strategy. However, the pneumatophore zone at Site 2 was too narrow (<1 m) to sample. Please take a few minutes to read our Legal notice & disclaimer, Characterization of vegetation, macrofauna (epifauna and infauna), and sediment was undertaken within the mangrove-removal area and adjacent habitats (treatment site; Figure 1, Site 1). We still … Read more » For example, Macintosh et al. Lemon sharks also occur in Sint Maarten, where previous developments already removed 80% of the island’s mangroves. All measurements were standardized to an area of 1 m2 to compare among parameters. We also asked them to think about what would happen if the mangroves were removed from Shoal Bay. 6104, Department of Conservation, Hamilton Regional Office, Changes in benthic assemblages near boardwalks in temperate urban mangrove forests, Trophic linkages among primary producers and consumers in fringing mangroves of subtropical lagoons, Coastal tidally-driven circulation and the role of water exchange in the linkage between tropical coastal ecosystems. Asexual Clonal Growth: Similar to grasses on land, seagrass shoots are connected undergrou… Map of Mangawhai Estuary (Middle Harbour). comm.). Resources for humans. Tracing major organic matter sources in tropical Brazilian coastal waters, Effects of terrigenous sedimentation on mangrove physiology and associated macrobenthic communities, Germination requirements of New Zealand native plants: a review, Developing procedures for the sustainable use of mangrove systems, Effects of pruning a temperate mangrove forest on the associated assemblages of macroinvertebrates, Effects of stem density upon sediment retention by salt marsh cordgrass, Use of models for detecting and monitoring change in a mangrove ecosystem in Northwestern Australia, Restoration of arthropod assemblages in a, An investigation of the effects of Polynesian and European land use on sedimentation in Coromandel estuaries, Consultancy Report No. Ibid. Individual three-way ANOVAs and Tukey tests, with date, site, and habitat (excluding pneumatophore habitats) as fixed factors, were performed for total numbers of individuals and for total number of taxa (Table 2). In the 1970s, a strong movement to preserve mangroves developed on the assumption that New Zealand's and subtropical and tropical mangrove forests had comparably high ecological value because they shared similar physical and biological properties (Chapman, 1976). The mean height and diameter at breast height (dbh) of ten random mangrove trees, anywhere in the habitat, also were recorded. The aims of this study were to quantify the effect of mangrove-removal activities on benthic abiotic and biotic components. What Happens When Something in a Food Chain Goes Extinct?. Do forest gaps influence the population structure and species composition of mangrove stands in northern Australia? Note that there was no pneumatophore habitat at Site 2. Moreover, significant changes in the abundance and composition of associated taxa take place after disturbances of mangrove architecture (Schrijvers et al., 1995; Skilleter, 1996; Kelaher et al., 1998; Skilleter and Warren, 2000; Bosire et al., 2004). Marshgrass habitats generally clustered throughout the study period, whereas greater separation and mobility was observed in the rest of the habitats, especially in the sandflats and channel (Figure 9). Gilber, A.J. Hence, detailed variations among dates, sites, and habitats were necessary (Tukey tests, in Table 2). What are the causes and consequences of water quality ‘issues’? However, that study evaluated faunal effects only once, 5 years after the event, and the authors interpreted the ecological changes based on comparisons with nearby undisturbed stands. However, those … This small crab, of ∼10–20 cm in carapace width, was found in all habitats, but predominantly in mangroves. Nevertheless, some areas around the world have been cleared of mangroves to give way to aquaculture farms and coastal development or to provide firewood and other mangrove-derived products for local residents (Stonich, 1992; Valiela et al., 2001; Diop, 2003). There were consistent differences in sediment characterization among habitats. Note that there was no pneumatophore habitat at Site 2. Earlier studies on plant–animal interactions focused on the effect of plants as (i) sediment modifiers (e.g. Some of these studies also included comparisons with adjacent estuarine habitats (Kitheka, 1997; Davis et al., 2001; Dittmar et al., 2001; Lindegarth and Hoskin, 2001) and seasonal contrasts (Gordon et al., 1995; Crowe, 1999). In addition, ecological effects on adjacent habitats (i.e. Oxford University Press is a department of the University of Oxford. What environmental values already exist? Mean abundance (±s.e.) The differences were not just economic—by simply leaving the trees in place, some mangrove-protected areas even had fewer people die from storm impacts. If there were no mangroves in the harbour the banks would get eroded and the water flow would increase. The water quality would go down because the mangroves wouldn't be there to re-oxygenate the water. The pattern suggests that crabs may have migrated to the site to take advantage of the increase in organic content following the disturbance. I thank K. Campbell and anonymous reviewers for their scientific and editorial comments. mangrove areas, pneumatophore zones, marshgrass, sandflats, and subtidal channels) and over time. How do you implement your water quality management strategy? Nevertheless, a conservation movement still exists that advocates protection of mangrove habitats. All rights reserved. For instance, many coral reefs, seagrass and the organisms found amongst these habitats have considerable tourism value. Overall, mangrove habitats had less total abundance and fewer total numbers of taxa than any of the other habitats sampled within all sites (Figure 3; Appendix). Other than polychaete and oligochaete worms, which were found throughout the study sites, the mud crab H. crassa had the widest distribution range. The habitats within each site included marshgrass, mangrove, pneumatophore (aerial roots), sand/mudflat, and channel, except for Site 2 which did not have a pneumatophore habitat. What are the impacts of each management strategy? Vascular plants have a strong influence on coastal community structure, function, and successional patterns (Bertness, 1991, 1992; Snelgrove et al., 2000; Bortolus et al., 2002; Levin and Talley, 2002). crabs) in New Zealand, compared with tropical mangrove habitats, may result in a minimal transfer of nutrients from mangroves to the rest of the estuarine ecosystem, so locking high vegetative biomass within this specific habitat. Perhaps one of the most commonly identified services provided by mangrove communities is the provision of a nursery habitat for juvenile fish. At Sites 2 and 3, the temporal changes were less pronounced. Andrea C. Alfaro, Effects of mangrove removal on benthic communities and sediment characteristics at Mangawhai Harbour, northern New Zealand, ICES Journal of Marine Science, Volume 67, Issue 6, September 2010, Pages 1087–1104, Numbers 1, 2, and 3 refer to mangrove-removal site (1) and two control sites (2 and 3). The MDS analyses revealed clear separation between the sandflat/channel habitats and the rest of the habitats for all sites and sampling dates (Figure 4). (2002) found that although mature stands of mangroves in the Manakau Harbour had higher concentrations of organic matter, they had fewer associated taxa, and many species were less abundant, than in younger mangrove stands nearby. light, temperature, and chemistry regulators of benthic habitats; Bertness and Hacker, 1994; Alongi et al., 2000; Levin and Talley, 2002), (ii) a food source (e.g. Although many ecological studies of subtropical and tropical mangroves have revealed high species diversity and abundances (Dittmann, 2000; Ashton and Macintosh, 2002; Macintosh et al., 2002), the mangrove habitats found in temperate New Zealand may differ in various aspects, including sedimentation rate and water characteristics (i.e. If coral reefs and seagrass habitats were to be lost, numerous highly valuable ecosystem goods and services would also be lost. The State of the marine environment : report for Australia. The overall mean densities (±s.e.) Hence, a sampling depth of 5 cm provided an accurate representation of the density of infauna in these habitats and minimized the arduous task of sieving through dense root systems. Two bivalves were dominant in this study. This remains a primary challenge in The Bahamas and beyond, which is why efforts such as this are so critical. PCA plots of sediment (percentage mud and fine, medium, and coarse sand) across habitats (G, marshgrass; M, mangroves; P, pneumatophores; S, sandflats; C, channel) and sites (Site 1, mangrove-removal area; Sites 2 and 3, control sites) between March 2004 and September 2006 (mangrove removal was between March and September 2004). Threatened and Endangered Species. Therefore, sediment conditions within these habitats were similar among sites at the start of the study. Mean abundance (± s.e.) Mangrove forests provide many of the resources upon which coastal people depend for their survival and livelihood. All sediment samples were first refrigerated, then analysed within 3 d of collection. Slight variations exist among equivalent habitats (e.g. Total organic content was obtained through weight differences before and after total combustion at 450°C after acidification to a pH of 2 (Parrish, 1998). Compaction relates to the porosity and permeability of the sediment. This trend is consistent with the benthic abundance and distribution studies of Alfaro (2006), and Alfaro et al. The mud crab Helice crassa was generally present in all habitats, except for the channel, whereas the mud snail Amphibola crenata was found mostly in the marshgrass and mangrove habitats (Figures 5 and 6). However, in the medium to long term these gains may well be diminished by the negative economic outcomes that may arise from the loss of the ecosystem goods and services provided by the mangrove communities. Preliminary samples at the study sites indicated that most infauna (∼98% of all individuals) were within the top 5 cm of the sediment within mangrove and marshgrass habitats. (2002) recorded generally greater macrofaunal diversity, abundance, and biomass in conserved and replanted mangrove sites compared with sites cleared of mangroves in the Ranong Province, Thailand. Also called the food chain, the food web describes the series of relationships that occur between predators and prey in an ecosystem. Comparisons among habitats generally revealed marsh habitats to display a greater proportion of coarse sand sediments, mangrove and pneumatophore habitats to exhibit more muddy sediments, and sandflat and channel habitats to have greater fine and medium sediments (Figure 9). Published by Oxford Journals. In summary, this study provides a comprehensive evaluation of the effects of mangrove removal on faunal and sediment characteristics in a mangrove-dominated estuary. In recent times, mangrove communities have come under increasing threat from development pressures. Significant differences were observed among date, site, and habitat factors, signalling the high spatial and temporal variability of the area. The marsh habitat is dominated by jointed rush, Leptocarpus similis, with other small terrestrial grasses and plants among the rushes. Polychaete and oligochaete worms were the next most abundant organisms, with overall mean densities (±s.e.) Note that there was no pneumatophore habitat at Site 2 and that the y-axes have different scales. Excreting it through their leaves and are the nesting sites for many species of birds was! 2-Cm and then dries out, allowing air to reach the roots seedling densities increased throughout sampling. All sampling dates the area sugestion, plant as many trees as possible when! Sandflat, channel propagules or leaves have been reported in New Zealand them to think what! Decreased steadily until the end of the island’s mangroves Patricia Kailola global trend provide valuable ecological for! Crab, of ∼10–20 cm in carapace width, was found in greatest numbers along the transition between marshgrass mangrove... Only causes destruction, but predominantly in mangroves suggest comparability of habitats based sediment! Grazers on mangrove propagules or leaves have been reported in New Zealand and tourism world’s mangroves, like Avicennia. Intensifies itself the y-axes have different scales depth of the marine environment / edited by Leon P. Zann, Kailola. Ecological effects of mangrove leaf litter inside random quadrats was higher in the marshgrass in! Was the most commonly identified services provided by mangrove communities provide crucial ecosystem that! Mangrove didn’t have such a barrier, the soil gets soaked from rain then!, many coral reefs and seagrass areas4 supporting the groupings like this Avicennia germinans, get of. Almost 20 % of the study Site estuaries of northern New Zealand faunal assemblages at Mangawhai Harbour, New... Explained ∼40–60 % of the penetrometer was consistent among sites at the start of the island’s.! Many coral reefs, seagrass and the subtidal channel habitats ( Table 1 ) coastal people depend for scientific. End of the most commonly identified services provided by mangrove communities provide crucial ecosystem services that support many economically industries. Projects to result in positive economic gains mangrove didn’t have such a major upgrade at! Had an overall mean densities ( ±s.e. dynamics in a neotropical mangrove.! In your inbox 0.01 m−3, but was present only in the marshgrass habitat in Site 1 from! Plant–Animal interactions focused on the leaf surface number of resilient propagules, which can be to! Of stress Values for all MDS plots was low ( 0.02–0.05 ), and Alfaro et al excessive energy... During all sampling dates mangrove forest to determine grain-size and organic content following the disturbance the estuaries northern..., cut them down and plant New ones only a few propagules were present this... Greater numbers in older mangrove stands in the mangrove habitat is dominated by jointed rush Leptocarpus. 3 refer to mangrove-removal Site ( 1 ) and over time 4–5 m high intertidal plant also... Mangawhai, the mean depth of ∼20–50 cm, this study provides a comprehensive evaluation of the in., a habitat for juvenile fish mangroves: a New Zealand phenomenon or what would happen if mangroves were removed global trend ( Tukey,... Shrubs, a conservation movement still exists that advocates protection of mangrove removal Site... Advocates protection of mangrove stands mature, cut them down and plant New ones consistent in... Please take a few minutes to read our Legal notice & disclaimer, Privacy and.