View source for Latitudinal biodiversity patterns of meiofauna from sandy littoral beaches

==Introduction==

This article is about latitudinal biodiversity patterns. The latitudinal biodiversity pattern of the meiofauna of sandy littoral beaches is discussed as a special case.


==Latitudinal distribution of marine biodiversity==

Large-scale patterns of marine biodiversity have been subject of many discussions (e.g.<ref> Rex M.A., Stuart C.T., Hessler R.R., Allen J.A., Sanders H.L. and Wilson G.D.F. 1993. Global-scale
latitutinal patterns of species diversity in the deep-sea benthos. Nature 365: 636–639.</ref> <ref> Rex M.A., Etter R.J. and Stuart C.T. 1997. Large-scale patterns of species diversity in the deep sea benthos. In: Ormond R.F.G., Gage J.H. and Angel M.V. (eds) Marine Biodiversity: Patterns and Processes. Cambridge University Press, New York, pp. 94–121.</ref> <ref name=A94> Angel M.V. 1994. Spatial distribution of marine organisms: patterns and processes. In: Edwards P.J., May R.M. and Webb N.R. (eds) Large-Scale Ecology and Conservation Biology. Oxford University Press, Oxford, UK, pp. 59–109.
</ref> <ref> Krause D.C. and Angel M.V. 1994. Marine biogeography, climate change and societal needs. Progress in Oceanography 34: 221–235.</ref> <ref name=G95> Gray J.S. 1995. Is coastal biodiversity as high as that of the deep sea? In: Olsen & Olsen (eds) Biology and Ecology of Shallow Coastal Waters. Olsen & Olsen, Fredensborg, Denmark, pp. 181–184. </ref> <ref name=G97> Gray J.S. 1997. Marine biodiversity: patterns, threats and conservation needs. Biodiversity and Conservation 6: 153–175. </ref> <ref> Gee J.M. and Warwick R.M. 1996. A study of global biodiversity patterns in the marine motile fauna of hard substrata. Journal of Marine Biological Assesment UK 76: 177–184.</ref> <ref> Heip C., Warwick R. and d’Ozouville L. (eds) 1998. European Marine and Polar Science (EmaPS), A European Science Plan on Marine Biodiversity. ESF (European Science Foundation) Marine Board Report. Strasbourg, France, 48 pp.</ref> <ref> Lambshead P.J.D., Tietjen J., Ferrero T. and Jensen P. 2000. Latitudinal diversity gradients in the deep sea with special reference to North Atlantic nematodes. Marine Ecology Progress Series 194: 159–167.</ref> <ref name=A> Allen A.P., Brown J.H. and Gillooly J.F. 2002. Global biodiversity, biochemical kinetics, and the energetic-equivalence rule. Science 297: 1546–1548.</ref>). These attempts to develop a general picture of diversity in the sea are hampered by the small number of key studies, the varied sampling protocols applied, the different diversity indices and the varying levels of taxonomic resolution <ref> Clarke A. and Crame J.A. 1997. Diversity, latitude and time: patterns in the shallow sea. In: Ormond R.F.G., Gage J.D. and Angel M.V. (eds) Marine Biodiversity: Patterns and Processes. Cambridge University Press, Cambridge, UK, pp. 122–147.</ref>. A general trend of species impoverishment towards the poles was reported for some taxa (e.g., corals, gastropods), but this does not hold for others (e.g., amphipods and decapods crustaceans) <ref> Dworschak P.C. 2000. Global diversity in the Thalassinidea (Decapoda). Journal of Crustacean Biology 20: 238–245.</ref> <ref> Bellwood D.R. and Hughes T.P. 2001. Regional-scale assembly rules and biodiversity of coral reefs.
Science 292: 1532–1534.</ref> <ref> Rodriguez J.G., Lopez J. and Jaramillo E. 2001. Community structure of the intertidal meiofauna along a gradient of morphodynamic sandy beach types in southern Chile. Revista Chilera de Historia Natural 74: 885–897.</ref>. In addition, it seems probable that there is a cline in increasing diversity from the arctic to the tropics, but the cline from the Antarctic to the tropics is far less well-established <ref name=G97></ref> since the Antarctic has high diversity for many taxa <ref> Clarke A. 1992. Is there a latitudinal diversity cline in the sea? Trends in Ecology and Evolution 7: 286–287.</ref> <ref> Starmans A. and Gutt J. 2002. Mega-epibenthic diversity: a polar comparison. Marine Ecology Progress Series 225: 45–52.</ref>. Broad latitudinal gradients in species richness are illustrated for [[Open ocean habitat|open-ocean]] pelagic and [[Deep Sea habitat|deep-sea]] taxa, but some debate continues to surround evidence for shallow-water systems, particularly for non-calcareous taxa <ref> Clarke A. and Crame J.A. 1997. Diversity, latitude and time: patterns in the shallow sea. In: Ormond R.F.G., Gage J.D. and Angel M.V. (eds) Marine Biodiversity: Patterns and Processes. Cambridge University Press, Cambridge, UK, pp. 122–147.</ref>. Gray (1997)<ref name=G97> </ref> stated that marine [[biodiversity]] is higher in [[benthic]] (bottom-related) rather than in [[pelagic]] (in the water column) systems, and on coasts rather than in the [[Open ocean habitat|open ocean]], since there is a greater range of [[Habitat|habitats]] near the coasts. A good comparison of multispecies [[macrofauna|macrofaunal]] assemblages inhabiting the same type of [[habitat]] (sublittoral, fine sediment bottom) showed little if any difference among tropical, temperate and arctic sites in terms of diversity<ref> Kendall M.A. and Aschan M. 1993. Latitudinal gradients in the structure of macrobenthic communities: a comparison of Arctic, temperate and tropical sites. Journal of Experimental Marine Biology and Ecology 172: 157–169.</ref>. There was some dispute on how far the observed latitudinal patterns are size-dependant and small bodied taxa (Protoza and meiofauna) tend to be more ubiquitous and their richness is less latitude dependant compared to large organisms<ref> Finlay B.J. 1998. The global diversity of protozoa and other small species. International Journal of Parasitology 28: 29–48.</ref><ref> Hillebrand H. and Azovsky A.I. 2001. Body size determines the strength of the latitudinal diversity
gradient. Ecography 24: 251–256.</ref><ref name=A> </ref>.


In coastal environments the interactions between coastal morphology, land-ocean exchanges, meteorological and tidal conditions, create a highly complex and finely scaled network of environmental boundaries. These boundary conditions explain why coastal waters have both higher species richness and a richer [[ecosystems|ecosystem]] than their oceanic counterparts <ref name=A94></ref>. [[Sandy shore habitat|Sandy shores]] are among the most ‘simple’ systems in terms of habitat complexity in comparison to other coastal ecosystems as, for example, rocky shores, algae and seagrass beds. [[Biodiversity]] and [[biomass]] of interstitial organisms are rather low. However, recent findings have shown that marine sands transfer energy very effectively, and that chemical and biological reactions take place faster there than in fine-grained sediments<ref> Boudreau B.P., Huettel M., Froster S., Jahnke R.A., McLachlan A., Middelburg J.J. et al. 2001. Permeable marine sediments: overturning an old paradigm. EOS 82: 133–136.</ref>. 


== Latitudinal distribution of meiofauna==

The maximum [[meiofauna]] densities reported in the study of Kotwicki et. al (2005)<ref name=K> Kotwicki, L., Szymelfenig, M., De Troch, M., Urban-Malinga, B. and Weslawski, J.M. 2005. Latitudinal biodiversity pattern of meiofauna from sandy littoral beaches. Biodiversity and Conservation 14: 461–474.</ref> ranged between 15 and 4312 individuals per <math>10 cm^2</math>. The reported densities rank among the meiofauna densities in sandy beaches reported in available literature. In general, high [[meiofauna]] density can be found in [[intertidal]] [[Mud|muddy]] [[Estuaries|estuarine]] habitats, while much lower values are recorded in the [[Deep sea habitat|deep sea]] <ref> Coull B.C. 1988. 3. Ecology of the marine meiofauna. In: Higgins R.P. and Thiel H. (eds) Introduction to the Study of Meiofauna. Smithsonian Institution Press, Washington, DC, pp. 18–38.</ref>. In fine sediments such as organic rich [[Mud|muds]], [[meiofauna]] densities of 104 individuals 10 cm sq and more are common <ref> Ellison R.L. 1984. Foraminifera and meiofauna on an intertidal mudflat, Cornwall, England: populations; respiration and secondary production; and energy budget. Hydrobiologia 109: 131–148.
</ref>.
The available [[meiofauna]] data showed a large within-site (within-region) variation in the temperate zone while there was very little variation within the [[meiofauna]] densities of the antarctic and arctic zones<ref name=K></ref>. These patterns demonstrate that attempts to project global [[biodiversity]] from the results of regionally based studies must include the significant variation in diversity among sampling sites. The low salinity effect on [[meiofauna]] occurrence was not clear – two brackish water locations have the same range of [[meiofauna]] density as full marine sites<ref name=K></ref>. As was reported in cited literature, the lower [[salinity]] was not associated with decrease of [[meiofauna]]<ref> Brown A.C. and McLachlan A. 1990. Ecology of Sandy Shores. Elsevier, Amsterdam, The Netherlands, 328 pp.</ref>.


In terms of taxonomical composition, the [[meiofauna]] taxa that were encountered during study of Kotwicki et. al (2005)<ref name=K></ref> are similar to those of [[Mud|muddy]] sediments. There were no [[meiofauna]] taxa found that were restricted to shallow permeable sediments only. The percentage composition, on the other hand, differed significantly between the different study sites along the latitudinal gradient. In general, nematodes dominate [[benthic]] [[meiofauna]] communities comprising more than half of the total [[meiofauna]] abundance. This was indeed the case for most sampling sites except for both polar regions (arctic and antarctic), where turbellarians were the dominant [[meiofauna]] group.


Some small [[macrofauna|macrofaunal]] [[crustacea|crustacean]] species (Cumacea, Amphipoda, Mysidacea) that can occasionally be found in [[meiofauna]] samples, were absent in the [[littoral]] zone of polar waters<ref name=K></ref>. Small size in [[macrofauna]] is often associated with a fast development, r-strategy and warm environmental conditions that permit fast egg incubation and growth<ref> Steele D.H. and Steele V.J. 1986. The cost of reproduction in the amphipod Gammarus lawrencianus Bousfield. Crustaceana 51: 176–182.</ref>. That strategy is unlikely to be fruitful in cold regions. These results support the hypothesis that warm regions support fast growing, smaller and more abundant organisms, and cold regions are dominated by larger and less abundant [[meiofauna]]. [[Macrofauna]] taxa may contribute to the [[meiofauna]] size class only in the tropics. A lower number of taxa was collected in both polar sites and, this in combination with slightly higher diversity in the temperate and tropic zones, supported the general pattern of diversity increase towards lower latitude. When only ‘[[meiofauna]] sensu stricto’ (i.e., without the small [[macrofauna|macrofaunal]] organisms) were taken into account, no clear latitudinal change could be found. 


==Meiofauna biodiversity of sandy shores==

However, data at species level can give a more detailed and perhaps different outcome. Average number of nematode species from sandy [[littoral]] sites ranges between 50 and 60 species in warm temperate localities (Italy), cold temperate (Baltic) and slightly less are reported from arctic Svalbard (Gheskiere, Ghent University, personal communication). The results of the classification illustrated the clear difference between the polar sampling sites on the one hand and the more temperate beaches on the other hand. Archambault and Bourget (1996)<ref> Archambault P. and Bourget E. 1996. Scales of coastal heterogeneity and benthic intertidal species richness, diversity and abundance. Marine Ecology Progress Series 136: 111–121.</ref> showed that large-scale heterogeneity explains a larger proportion of the variance in [[macrofauna]] species richness than substratum heterogeneity on a more local scale. In this context, it is fairly reasonable to refer to the important human pressure on temperate beaches. Recent studies (e.g.<ref name=W> Weslawski J.M., Urban-Malinga B., Kotwicki L., Opalinski K., Szymelfenig M. and Dutkowski M. 2000. Sandy coastlines – are there conflicts between recreation and natural values? Oceanological Studies 24: 5–18.</ref> <ref>Gheskiere, unpublished data</ref>) focused on the effects of recreational pressure (trampling, beach cleaning and nourishment). Weslawski et al. (2000)<ref name=W></ref> suggested that a highly diverse [[meiofauna]] and diatom assemblage in undisturbed beaches may act as an effective biological filter for some types of pollutant, while less diverse, but more abundant biota in disturbed areas are more effective in processing organic matter (self-cleaning of the beach). Largely as a result of conflicting uses of coastal habitats, losses of marine diversity are highest in coastal areas. The best way to conserve marine diversity is to conserve habitat and landscape diversity in the coastal area. Marine protected areas are only a part of the conservation strategy needed. A framework for coastal conservation should include integrated coastal area management, where one of the primary goals is sustainable use of coastal [[biodiversity]]<ref name=W></ref>.


==Related article==

* [[Sandy shore habitat]]


==References==

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{{author
|AuthorID=5254
|AuthorName= Lechu
|AuthorFullName= Kotwicki, Lech}}


[[Category:Marine Biodiversity‏‎]] 
[[Category:Coastal and marine ecosystems]]   
[[Category:Beaches]]