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To browse Academia. Skip to main content. By using our site, you agree to our collection of information through the use of cookies. To learn more, view our Privacy Policy. Log In Sign Up. Download Free PDF. Mark Hay. David McNeely. Mark Bertness. Download PDF. A short summary of this paper. T ft, u bng time, seagrass communities remained. Uniformly green and almost impenetrably dense, seagrass beds hide the life teeming within them very well.

The s brought an explosion of research, and the abundance of organisms within seagmss communities became widely acknowledged among marine scientists. This question has dominated seagrass community ecology and is the framework for this chapter. Within the general question of habitatutilization and function, we chose to focus on severalspecific topics in marine community ecology to highlight significant contributions from seagrass studies. First, some of the most comprehensive analyses of detrital food webs originated from seagrass beds, along with salt marshes.

At least half of the prodigious primary production of seagrasses enters the food drain as detritus. Seagrass studies helped to establish stable isotopes as food web tracers in ecology.

Second, seagrass studies demonstated that inconspicuous but higtrly productive and palatable microalgae provide an important source of food for consumers. Third, seagrass beds provide some examples of appar.

Fourth, seagrass studies have contributed greatly to r. Fifth, recent experimental manipulations in seagrass beds have provided examples of the complex nature of ecological interactions between native and non-native species. Until recently, knowledge about marine non-native species has been limited primarily to their distribution, abundance, and perhaps origin, and ecological interactions have only been hypothesized Steneck and Carlton, this volume.

Finally, seagnss communities provide some of the most comprehensive examplesof the acid test of ecological understanding-marine habitat restoration. Seagrass community research is driven increasinglyby the accelerating loss of seagrass habitat and associated species of economic value and, in the United States, the legislative mandate to mitigate intentional loss of seagrass ecosystems Orth and Moore ;Robblee et al.

Ecologists need to understand the community consequences of seagrass decline. Mechanistic understanding of the communityis required for effective mitigation and restoration and to achieve ecological functions e.

What kinds of functions lead to the biological weafth of relatively undisturbed seagrass beds? Seagrasses are donal marine flowering plants and occur in shallow softsediment habitats along the shores of bays and estuaries throughout most of the world. The notable exceptions are the surfgrasses Phyllospadix spp. There are between 5G seagrass species in the families Hydrocharitaceae and Pota-mogetonaceae.

Seagrasses are Primariiy subtidal' but they cariextend also into the intertidal zone. In subtropical and tropicai meadows, several seilgrass species. On the northeast coast of Japan, five species of eelgrass ctccut each wiill a distinct growth form, and up to three sgtecies e-g. Williams Pers. All seagrass beds also include many kinds of algae' Algal epipht'tes use seagrass leaves and rhizomes as substrata and m.

For example, Humm t"io. The epiphytes composed ft::" t Zostera asintica Zostua caesPitosa clump diameter FreeJiving macroalgae as well as periphytic forms grow from rocks and shells.

In temperate beds, large canopy-forming rockweeds Cy st oseira, Fucales and kelps Egregin, Laminarin , as well as surfgrass, grolv on numerous small few mz rock outcrops. In hopical seagrass beds, over a dozen species of siphonous green algae Caulerpales , which grow from rhizoids anchored in the sediments, form a major component of the communify.

Attached macroalgae often break off and form large, drifting clumps and mats that are important components in the community. The common macroalgae in drift mats alone represented 13 species of green, brown, and red seaweeds in one study Williams Cowper Although the seagrass canopies strongly attenuate light, benthic microalgae also occur commonly in seagrass communities. Animals in every major Phylum occur within seagrass beds.

Animals pack the complex belowground mat of seagrass roots and rhizomes and live attached to or dosely asso. More mobile snails, crabs, and fishes cruise tfuough or above the leaf canopy. Seagrass beds also support large populations of migrating waterfowl such as herbivorous swans, ducks, ancl gee! Raptors strch as bald eagles and ospreys feed over the beds.

Large vertebrate grazers such as green turtles, dugongs, and manatees rely on seagmss beds for food and habitat; some of these species are threatened or endangered.

The majority of the coinmercially valuable marine species in the United States are founC tr. This research has broadened the understanding of how marine plants and animals interact' Herbivory has domlnated the srudy of marine plant-animal interactions, and seagrass studies certainly have contributed to this topic. ExtendLg be,v'ond herbivory seagrass studies have prwided some of the best examples of nontrophic interactions, both positive and negative e'g', ferfrlizatioo bioturbation , that ilso control the distribution and abundance of associated organisms.

Although many animals di' rectly consume seagrass leaves McRoy and Helfenich ;Ogden ;Thayei et al. Although rhizomes have high caloric values Girch , we l. Belowground biomass forms detritus as the older distal end dies and is reptaced by the terminal rhizome meristem Tomlinson L The importance of detritus in seagrass beds was inferred for a long time because of the sheer amount of detritus formedu'.

Confirmation ofthesourceofplantdetritusisdifficultbecauseitisbasically unidentifiable once in a consumer's gut' Howevet detritus retains the unique stable isotope signature laid down by the plant's ph,vsiology, and thus stable isotopes can be used to differentiate the source of the primary production at successively higher levels in the food web.

Stable isotopes also helped in determining situations where other primary producers become more irnportant Stephenson et al. Ruckelshaus et al. Algal epiphytes have very high biomass-specific rates of primary production and can. Altirough very few studies have directly assessed the nutrifional content of epiphytes Nichols et al.

Most of the mesoconsumers such as caprellids and gammarids are small enough to select algae from the epiphyte matrix, which also includes sediment particles and dekitus Harrison l;Zimmerman et al.

Because consumers select algae from the matrix, values for organic content, proteins, and carbohydrates derived from the intact matrix probably underestimate its nutritional quality for the meso' and micrograzers.

Trophic lnteractionsAlthough the focus on detrital food webs mightpredominate in seagrass ecology, it was always apparent that seagrass vegetation and the associated community could be conholled by herbivores because of dramatic examples of overgrazing by large invertebrates such as sea urchins Camp et aL. Despite these dramatic examples, there has been a tendency to treat herbivore contol of seagrasses as an anomaly.

It has been argued that a historically important top predator was missing in the case of sea urchins or that the environment represented some otherwise "special case. In addition to controlling the distribution and abundance of seagrasses, animals also influence the population biology of clonal seagrasses. The influence of herbivores on the population biology of seagrasses represents a relatively unexplored research area, but one with some interesting parallels to terrestrial ecosystems such as grasslands with intense grazing.

After adjustment, the remaining ungrazed shoots can exhibit increased rates of photoslmthesis and production of nitrogen-rich young leaves. The new growth is higherquality forage for sea turtles, which repeatedly retum to feed on it Bjomdal ;Thayer et al.

Because intemal adjustments to graztng cannot be sustained indefinitely, there is a broad range of plant responses to grazing intensity. For example, heavy grazing by sea turtles Williams , sea urchins Heck and Valentine , and dugongs Preen can lead to reduced seagrass standing crop, and intense grazing during fall and winter can lead to local disap-Scrr.

Similarlv seven seagrass species in a variety of locations, subjectgd to a one-time experimental cropping of up to oo of the abor,'eground shoot biomass, showed little evidence of negative effects on-regrowth rates. Instead, regrowth rates at the highest levels of cropping were often greater than those with lower rates of biomass removal Cebri6n et al. Just as noted in terreskial systems McNaughton ;Belsky ;Huntley ;Herms and Mattson , there is a continuum of seagrass responses to grazing pressure, ranging from negligible effects on shoot production at low intensity, to stimulatory effects at intermediate intensily and negative effects at high intensity.

Although the ability of seagrasses to withstand grazingpressure appears to be related to the amount of belowground rhjzome storage capacity Dawes and Lawrence ;Dawes et aL. Animals also can influence the sexual reproduction of seagrasses. Polychaetes inhabiting eelgrass inflorescences Hellwig-Armonies prey upon flowers and seeds M.

Hemdon, pers. Although there are few published studies on seagrass seedling recruitment in the field, seed predators can limit seedling recruitment Fishman and Orth Nthough herbivores defoliate seagrasses, they also can exert a positive effect on seagrass population growth rates, persistence, and, conceivably, genetic diversity.

Animals, by creating gaps in the canopy, can enhance the recruitment of seagrass; seed germination and seedling suwivaLfor Zostera spp. The view that seagrass communities are not controlled by consurners recently achieved the status of a paradigm, with the advent of declines in seagrass vegetation Orth and Moore ;Short et al.

Hence, emphasis has been placed on physicochemical control of seagrass communities. Howevet the issue is more complex and interesting when subtle biological interactions between seagrasses, shading epiphytes, herbivores, and perhaps top predators are considered.

Mesoherbivores clearly can control the growth of seagrass leaves by removing epiphytes Neckles et a1. Grazers similarly can controi macroalgae that bloom in re-sponse to eutrophication Hauxwell et al' ' Epiphytegrazer interactibns need to L. FGhermore, the assumption that epiphyte-associated declines in seagrasses are due to trottom-up control by eutrophication needs to be evaluated against altemative hypotheses' For example, the papers cited in the preceding paragraph indicate that mesograzers can and do control epiphyte biomass' Mesograzers can exhibit nonlinear functional responses to in-.

In addition, Edgar lggg ,after estimating food consumption by amphipods and gastropods, concluded that mesograzers are probably foodtimitea inAustalian seagftrs meadows. This raises the question of why mesograzers do not respond sufficiently to the eutrophication-induced algal proliferation to ultimately reestablish grazer contol. An altemative to the conventional wisdomof bottom-up control of seagrasses in eutrophic mvironments may provide the explanation that overfishing of top predators might lead to a cascading effect in whiclr epiphytes are released from grazing when small fuhes increase and in turn control the abundance of meso-and microherbivores, suctr as isopods, caprellids, and amphipods Figurc 12'3 ' Data in partial support of this altemative hypothesis have recently been published Fleck et al.

In developing a general understanding of trophic interactions and community structure e. On a gradient of primary production Oksanen et al. As discussed abov'e, the wide variation between the relative importance of detritus versus living plants in supporting food webs should be useful in evaluating the effects of detritus and omnivory on hoPhic structure. There is excePtional functional diversity at the primary producer level because seagrasses themselves vary in nukitional value Birch ;Irving et al.

This plant diversity can facilitate coexistence among very similar species of sea urchin consurners Keller The combination of vascular plants and diverse forms of algae might also explain why seagrass beds not only support most of the kinds of animals found in the rocky, intertidal seaweed beds and unvegetated soft sediments, but also sea turtles, sirenians, and waterfowl not tyPically found in these other communities.


Byers, J. Marine parasites and disease in the era of global climate change. Annual Review of Marine Science Advanced copy PDF. Gribben, P. Comparative biogeography of marine invaders across their native and introduced ranges.

by Mark Bertness: Marine Community Ecology and. Conservation. ISBN: #​ | Date: Description: PDF-c2cb5 | Marine Community.

Marine Community Ecology and Conservation

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Marine Community Ecology: The Views of Many

A compelling evolutionary narrative that reveals how human civilization follows the same ecological rules that shape all life on Earth Offering a bold new understanding of who we are, where we came from, and where we are going, noted ecologist Mar A compelling evolutionary narrative that reveals how human civilization follows the same ecological rules that shape all life on Earthi Offering a bold new understanding of who we are, where we came from, and where we are going, noted ecologist Ma Anna Shaffer, Marine Ecology In the second edition of Marine Community Ecology and Conservation, Bertness and co-editors provide an update of the dominant elements of marine community ecology as well as the now maturing science of our generation: conservation. The editors state that the book is intended to fill intellectual gaps and update readers on new developments in applied ecology in the oceans. The book targets upper-level undergraduate to graduate level users. We feel that the book achieves this goal and is a very useful resource for graduate-level readers.

Bruno, J. Harley, and M. Climate change and marine communities. In: Bertness, M.

Bertness, M. The Ecology of Atlantic Shorelines. Gaines, and M. Hay Editors. Marine Community Ecology. Nybakken, J.

In the second edition of Marine Community Ecology and Conservation, Bertness and co-editors provide an update of the dominant elements of marine.

The first explores processes that generate pattern in benthic communities. The middle examines the ecology of specific marine benthic community types, ranging from rocky shores and soft substrate habitats to kelp forests and coral reefs. The close examines conservation and management issues, emphasizing how profoundly marine communities are impacted by humans" Bruno, J.

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Books Edited Bertness, M.

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As a global organisation, we, like many others, recognize the significant threat posed by the coronavirus.

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There is a widely-observed trend towards species-rich, highly diverse communities at environmentally healthy sites (Birkeland , Bertness et.

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Marine Community Ecology and. Conservation. M.D. Bertness, J.F. Bruno, B.R. Silliman, J.J. Stachowicz. (Eds). Sunderland, MA: Sinauer Associates Inc.,