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Home , Marine habitats, Seagrass, Seagrass meadow

CHAPTER 8

COASTAL SALTWATER

Charles Birkeland

The Interacting Seascape of soil from land has a detrimental effect on diversity, and size distribution. The The most productive, diverse and dynamic amount of living coral cover is directly related to the are found where the land and meet the . The amount of terrestrial vegetation because the pre- three primary ecosystems— stands, sea- vent erosion. Mangrove stands and grass meadows and coral reefs—are the areas with the trap soil. Mangrove stands buffer the fl ow of fresh- highest gross primary (Table 8.1). Here and chemical to the sea. Coral reefs is also where is greatest at the higher lev- protect coastal lands from waves and construct els of taxa. Coral communities are composed of coastlines in response to changes in sea level. The 32 phyla of animals, whereas only 17 phyla are found three coastal habitats have substantial favorable ef- in terrestrial and freshwater ecosystems of the world, fects on each other. and of these 16 are also found on reefs. (Ony- chophora are found only in tropical rainforests.) The All three coastal habitats export , but a rela- complex mosaic of interacting ecosystems on tropical tively small amount in proportion to their gross pri- is an important component of diversity that has mary productivity is useable by humans and other an- a vital role in the of the region. The dynamic imals. The trophic interactions among the organisms coastal habitats contribute to the physical structure of of different coastal habitats are complex. Mangrove the coastlines. While the coastal ecosystems are resil- stands and seagrass meadows act as nurseries for cor- ient and provide structure and protection from the sea al-reef fi shes. are transferred from seagrass and from the uplands, they are also the systems most meadows to coral reefs by fi shes and exposed to infl uences of erosion and pollution from which forage for food on seagrass meadows and use the land and storm waves from the sea. In all three coral reefs for shelter. The by fi shes and in- coastal ecosystems, the structural complexity and geo- vertebrates from coral reefs shapes the seagrass mead- morphology of the coastlines they create and the tro- ow by creating bare spaces near the reef. The boundar- phic interactions among habitats are the keys to un- ies or edges among these three habitats are especially derstanding the distribution and abundances of the di- rich in because of the trophic exchanges and verse organisms they support. shelters provided among them.

Physical Interactions Among Coastal Ecosystems Unfortunately, the best habitats for productivity, di- versity, and coastal formation are also the most attrac- The three major types of ecosystems (, sea- tive and logistically effi cient for human settlement and grasses and coral reefs) are distinct coastal features. activity. Both natural and anthropogenic disturbances They function in relation to the bordering terrestrial are focused at the boundaries of the three coastal eco- and off- marine ecosystems and are all strongly systems. The effects of cyclones are greatest where the interdependent. waves and spray of saltwater impact the and the effects of from erosion are greatest on Biodiversity Assessment of Tropical Island Ecosystems 140 Coastal Saltwater Ecosystems

Table 8.1. Average gross primary productivity in terrestrail and (from Lugo and Snedaker 1974; Crisp 1975; Lewis 1977). Gross primary productivity (g C m-2 yr-1) Mangrove forest1 2300-5074 Tropical seagrass bed 4650 4200 Tropical algal 3836

Peru current 3650

Sugar cane fi eld 3450 Sewage treatment 1800

Kelp bed 1750 Spartina 1600 Estuarine 1320 Temperate algal community 920

Coniferous 800 Deciduous woodland 785 Mangrove forest2 511 Field grass 500

Long Island Sound 470 Eutrophic lake plankton 75-250 English Channel plankton 135 Sargasso Sea plankton 134 plankton 100

Open near coral reef Barbados 50 Rongelap Atoll 28 Hawai`i 21-37

Oligotrophic lake plankton 7-25

1Receives wet season terrestrial runoff. 2Lacking obvious external nutrient sources. Biodiversity Assessment of Tropical Island Ecosystems Coastal Saltwater Ecosystems 141 the nearshore marine habitats. The sea-level rise from be residing outside the habitat (Birkeland 1985, Ogden global warming will have the greatest impact on coast- 1997). Traditionally, foodwebs have been described al habitats. Sixty percent of the human population within ecosystems and habitats, but in the coastal hab- lives within 50 miles of the coast. The self-repairing itats, species outside the system may actually “domi- protective services of coastal habitats are nate” the energy fl ow and community structure. Third, being replaced with less stable human constructions although mangrove forests, seagrass meadows and at an increasing rate. For example, the human mor- coral reef communities are among the most productive tality from tropical cyclones in the Sundarbans man- ecosystems in the world in terms of gross primary pro- grove region of Bangladesh increased dramatically as ductivity (Table 8.1), less than 10% of the net produc- the mangroves have been harvested and humans have tion is processed into the through herbivory moved into the “reclaimed” land. Even the term fre- (Birkeland 1985, Harrison and Mann 1975, Hatcher quently used, “reclamation,” is inappropriate for ac- 1997, Kirkman and Reid 1979). Despite the diversity quisition of land that was originally created by man- and abundance of living in these habitats, grove stands or coral reefs. nearly all net production from the main framework species goes directly to the detrital food web. Even The coastal ecosystems are also dynamic in the sense though most of the energy is transferred within and be- that natural disturbances and disruptions occur at in- tween coastal marine habitats by detritivory, the infl u- tervals that are frequent relative to the age of the foun- ence on community structure is often mainly through dation species. For example, corals create the physi- herbivory (Birkeland 1985, Ogden 1997). cal structure of coral-reef ecosystems and individual colonies can experience hurricanes, a crown-of-thorns The reason that energy fl ow is mainly through detriti- outbreak, water warming, serious sedimentation, dis- vores rather than herbivores is because of resistance of ease and other major events in their lifetimes. Coral- to direct consumption. Mangrove reef communities probably never reach what ecolo- are particularly resistant to digestion by herbi- gists conceive as equilibrium or climax communities. vores or to by microbes because they Superimposed on this are the matters with which we contain tannins. Tannins form complexes with pro- are most concerned, i.e., what changes are results of tein and thereby inhibit the action of enzymes (Gold- human activities? In order to distinguish the effects stein and Swain 1965). By forming loose complexes of natural events from the effects of human activities, with protein molecules by hydrogen bonds and per- we need to have a solid understanding of the back- haps some covalent bonds, tannins inhibit the decom- ground natural variability. A monitoring program will position of mangrove leaves by microbes (Benoit and determine the magnitude of change, the frequency and Starkey 1968, Cundell et al. 1979, Zucker 1983) and duration of change, and the causal processes of the fungi (Williams 1963, Zucker 1983), inhibit the diges- changes (see the Monitoring section). Before monitor- tion of mangrove leaves by (Feeny 1969) ing can be done, the spatial extent of the habitat and and vertebrate (Glick and Joslyn 1966) herbivores, an inventory of the species of organisms that are there and inhibit the productivity of in must fi rst be accomplished (see the Inventorying sec- in a mangrove (Smayda 1970, Kutner 1975). tion). Although the gross production of mangroves is very high, the tannins greatly delay and inhibit its direct Biological Interactions Among Coastal Ecosystems consumption. The loose, generalized, nonspecifi c and variable nature of the hydrogen-bond attachments by At the start of analysis of coastal ecosystems, we tannins to enzymes and other proteins make it improb- should make clear three important concepts. First, able that organisms could evolve specifi c detoxifying mangroves, and stony corals are “founda- mechanisms to tannins (Feeny 1970, 1976; Rhoades tion species,” the organisms that defi ne the habitat and and Cates 1976) as they do to other chemicals of provide the physical structure to the ecosystem. They defense such as alkaloids (Hodgson et al. 1965, Feeny actually cause the formation of the geological founda- 1976). tion of the habitat or at least solidify the substratum on which the ecosystem is structured. Second, the spe- Seagrasses evolved from terrestrial plants that rein- cies having the major infl uence on the boundaries and vaded the sea. Sea turtles, geese and ducks, and du- characteristics of habitats and species having impor- gongs and are herbivores that evolved from tant contributions to the energy input to habitats may terrestrial vertebrates that reinvaded the sea. There- Biodiversity Assessment of Tropical Island Ecosystems 142 Coastal Saltwater Ecosystems

fore, these herbivorous vertebrates have the biochemi- photosynthetic fi xation of CO2 that was taken (Park cal equipment to feed heavily on seagrasses. Marine and Epstein 1960). Plants using the C4 photosynthetic invertebrates and fi shes, on the other hand, often have pathway tend to incorporate a greater proportion of 13C much seagrass material in their stomachs, but chem- isotope and plants using the C3 pathway incorporate a ical analysis demonstrates that the seagrass material greater proportion of 12C isotope. Animals have been usually passes through largely undigested. It is gener- found to have the same isotope ratios in their ally the epiphytic algal and bacterial organisms that bodies as in their diets. The milk and hair from cattle are digested. Fenchel (1970) found the amphipod Par- in meadows of C3 or C4 plants have carbon hyella whelpleyi to feed on detrital seagrass (Thalas- isotope ratios that correspond to their dietary differ- sia testudinum), but the plant material actually passed ences (Minson et al. 1975). through the amphipod undigested. Only microorgan- isms living on the surface of the detrital material were Like mangrove forests and seagrass meadows, cor- assimilated. Randall (1961) found 81% by volume of al reef systems demonstrate a very high gross pro- the stomach contents of the Hemiramphus ductivity, but proportionately little is usable export brasiliensis was composed of seagrass. Likewise, Bell (Hatcher 1990, 1997; Crossland et al. 1991). Of ex- et al. (1978) found three species of monacanthid fi sh- cess production, approximately 15% is accumulated es consumed considerable amounts of seagrass which in reef community structure, about 75% is exported in comprised up to 65% of stomach contents. However, unusable form (, dissolved organic material), Bell et al. (1978) found only the epiphytic and leaving about 10% (35 million metric tons per year encrusting animals were being digested. globally) that could be potentially harvested (Cross- land et al. 1991). This is substantially less than 1% of There are some interesting exceptions. The mysid the gross of coral reefs globally Mysis stenolepis is abundant in seagrass mead- (Hatcher 1997). Detritus comprised 95% and 85% of ows and it has been indicated by studies with car- the stomach contents of and larvacean tu- bon isotope ratios that M. stenoleis can assimilate the nicates, respectively, in Enewetak Atoll (Gerber and structural cellulose from seagrass with 40% effi ciency Marshall 1974). A substantial proportion of the stom- (Foulds and Mann 1978). When the mysids were treat- ach contents of planktivorous reef fi shes at Enewetak ed with antibiotics, they lost the ability to digest cel- also consisted of detrital fragments of benthic algae lulose. They reqained the ability after being fed fresh (Gerber and Marshall 1974). How much of the coral- mysid guts. This implied that M. stenolepis is able to reef food web is founded on detritus produced by pho- assimilate seagrass by hosting microbes in its gut that tosynthesis of (e.g., coral mucus) and are capable of digesting cellulose (Mann 1982). Ad- how much from benthic (detrital frag- ditional carbon isotope ratio studies have shown that ments of benthic algae) remains unknown and should the mangrove-dwelling gastropods Ellobium sp. and be investigated. Crassidula sp. also obtain a substantial portion of their diets from mangrove litter (Wilkinson 1994). Assessing Habitats and Since mangrove, seagrass, Spartina and other vascular Communities plants of terrestrial origin are so productive, yet gener- ally refractory for decomposition or digestion by ma- Habitat Distribution and Patch Size rine organisms, it is important to determine how much of this material actually enters the marine detrital food Mangrove stands, seagrass meadows and coral reefs web if we want to understand the coastal ecosystems. are being cleared and converted for human use at A method has been developed by which the paths of an accelerating rate. Over 50% of the mangroves in carbon fl ow can be found by examining the tissues Southeast Asia have been removed, mainly for exca- of animals from various places in the food web. The vating the area for fi sh and shrimp . In the Phil- method involves determination of the stable carbon ippines nearly 80% have been removed and in Singa- isotope 13C:12C ratios in animal and plant tissues (Park- pore over 99% of the mangroves are gone (Winkinson er 1964; Smith and Epstein 1971; Land et al. 1975; 1994). Initially, operations relied on local- Haines 1976; Thayer et al. 1978; McConnaughey and ly caught wild larvae from mangrove stands to seed McRoy 1979a,b). Plant species differ in their 13C:12C shrimp ponds for aquaculture. But as the mangrove ratios in a manner which relates to the pathway of stands were eliminated, it became necessary to rear Biodiversity Assessment of Tropical Island Ecosystems Coastal Saltwater Ecosystems 143 larvae in the laboratory. In the 1990s, viral infections However, the resolution of satellite imagery is not devastated the monoculture shrimp stocks in ponds nearly as sharp as that of aerial photography. The res- world-wide and because mangrove stands were no olution is best in Landsat and SPOT satellites with longer available to trap , the shrimp ponds blocks 10 to 20 m per side. With relatively low resolu- fi lled with and decreased be- tion, small areas may be omitted or their size may be cause of . At the same time, coastal fi sh- exaggerated. Exaggeration occurs when several small- eries showed similar declines, possibly in part because er areas are merged. of the elimination of the mangrove stands and their nursery services. Tropical coastal aquaculture is often “Ground-truthing” is necessary for interpreting and a boom and collapse economy. validating any remote-sensing technique. This involves visiting several sites and comparing the remote image Because of their depth, shrimp ponds do not easily re- with the actual feature in the fi eld. The fi eld observa- cover to mangrove stands. Likewise, dredged areas of- tions should have accurate geographical coordinates. ten do not recover to coral reefs because the pits ac- This is usually done with a Global Positioning System cumulate sediment. When outboard motors churn up (GPS). These have become accurate and convenient in the sediment in a seagrass , it often leaves a the past couple of years. The Garmin 48 personal GPS permanent trail because seagrass partially relies on the can determine and relocate a site on Earth within about bacterial communities and the chemical nature of the 8 m and can be carried in a pocket. substratum near the runners of mature seagrass beds. Therefore it is of primary importance to document the Aerial photography has been available as early in magnitude and rates of decline of these ecosystems. 1925 on the . Sir Maurice Yonge, in the fi rst Great Barrier Reef Expedition, used aerial The primary functions of monitoring are to detect photographs extensively in a ground-truthing. It was change and to determine the causal factors that pro- only since the Second World War, in the mid 1940s, duce these changes. The changes in distribution and that aerial photography of coral reefs and other coast- extent of mangrove stands, seagrass and coral reefs al communities has been widely developed and made over time can be made by comparing aerial photo- available. Satellite imagery for vegetation mapping graphs and/or satellite images from the present with has been available since the launch of the fi rst Land- aerial photographs, satellite images, or maps from the sat in 1972. past (Chapter 11). Aerial photography is the most pow- erful tool for high resolution, with scales to 1:2,000 Aerial photographs from the past, which might be used allowing measurements of subjects as small as one- for comparison with more recent aerial photographs to meter in diameter. (Scanning Hydrographic determine the nature of changes in coastal habitats in Operational Airborne LIDAR Surveys, with LIDAR the past half century, might be obtained from the com- meaning LIght Detection And Ranging) surveys can pany Air Surveys Hawaii, from the Bishop Museum, produce high-resolution three-dimensional documen- from the U.S. Army Corps of Engineers, USGS EROS tations of the geomorphic patterns of coral-reef struc- (Earth Resources Observation System) website, and ture, commonly down to 35 m or deeper, depending from the NOAA website. on water clarity. Computer software can rotate the LI- DAR image in three dimensions. The images can also The patch size of seagrass meadows and the percent be produced by off-set color printing, with observation living coral cover should be measured. The function of through 3-D glasses. habitat can be related to their fragmentation, patch size and distribution. Mangrove stands, seagrass meadows Satellite imagery has the advantage of recording large and coral reefs do not perform their functions if too areas frequently and regularly. The imagery can cover small. a wide variety of spectral bands which allow the inter- pretation of photosynthetic activity and primary pro- Topographic Complexity ductivity over a large area. A summary of the sensor specifi cations of the main satellites used in vegetation The standard method for measuring topographic com- mapping are given by Spalding et al. (1997: 18). plexity is to fi rst stretch a line taut between two points. Then another line or fi ne chain is laid along the con- tour between these two points, in continuous contact Biodiversity Assessment of Tropical Island Ecosystems 144 Coastal Saltwater Ecosystems with the substratum. The contour length is divided by the isobath at the desired location and recording the the straight distance to give a comparative index of distance of each category of items covering the sub- topographic complexity. stratum. The objectives of the Line-Intercept Transects Coral and Other Sessile (LIT) are limited to questions concerning percent cov- er or relative abundances. Information from LITs are Benthic Communities not appropriate for determining demographic param- eters such as growth, , or mortality. The Rapid Assessment of Large Areas: Manta Tow Point-Quarter Plotless Technique or permanent quad- rats are more appropriate for demographic questions. Some phenomena that cause large-scale changes, e.g., crown-of-thorns outbreaks, , diseases, Percent Cover in 25-Cell Quadrats storm damage, dynamite fi shing, and derelict nets are patchy and can be overlooked by surveys with detailed The 25 cells in the Point-Intercept Quadrat described quantitative focus. It is not unusual that investigators above each constitute only 4% of the area under the are so well trained in standard coral-reef survey tech- quadrat. If living coral cover is the main parameter niques such as transects, quadrats and plotless sam- of interest, then a rapid and effi cient method of esti- pling techniques that the major events are on too large mating the living coral cover is by tallying the total a scale to be assessed at all. The Manta tow survey is a percent cover for each species under the quadrat each method for rapidly surveying large areas in a relative- time it is tossed. Estimation to the nearest percentage ly short time. Manta board towing involves having an is relatively accurate because one percent is one quar- observer or an observer with a video camera on a fl at ter of each cell. This method is, of course, not useful board attached to an outboard motor boat with a rope. for other parameters such as size distribution. The boat pulls the manta board and diver along an iso- bath for a given unit of time, usually 2 minutes. The Point-Quarter Plotless Sampling board is used as something for the observer to hold on to, as a way to direct the depth and direction of move- To survey by the Point-Quarter Plotless Sampling ment by changing the plane of the board, and provides method, one tosses a rock hammer or other object a place where a writing sheet or scoring panel and pen- that can perceive to have four quadrants. Then with a cil can be attached for recording data. This system has seamstress’ measuring tape, the distance to the nearest the advantages of not requiring expensive equipment, coral in each quadrant, as well as the maximum diam- extensive training, or major support in remote loca- eter and the maximum diameter perpendicular to the tions. The techniques are briefl y described. They are main diameter are measured. From these three mea- explained in detail by English et al. (1997:14-33). surements for each coral in each of the four quadrants, size distributions, population densities, percent living Point-Intercept Quadrats coral cover, frequency and diversity can all be calcu- lated. This method is best for determining size distri- If it is important to include small and rather amorphous butions of coral colonies. Each of these parameters benthic biota such as fi lamentous algae, crustose cor- can be calculated both for the entire community and alline algae, fi lmy encrusting and ascidians, for each species. The Point-Quarter Plotless Sampling the Point-Intercept Quadrat method is the easiest to method is thoroughly described in UNESCO (1984) use. This consists of a square quadrat frame with four and in Birkeland and Lucas (1990). (See also Chap- lines evenly space across both pairs of sides, giving 25 ter 3, The Point-Centered Quarter Method, p. 32-33 in cells or 16 intersecting lines. The organisms directly this Manual.) underneath each of the 16 points are tallied on under- water paper each time the quadrat is tossed. Size Categories in the Transect Strip

Line-Intercept Transects The most rapid method for obtaining data on size dis- tributions of corals is to measure the maximum diame- The Line-Intercept Transect is traditionally the meth- ter of all corals with their centers within 0.5 m of each od most widely used for corals. It is described in detail side of the transect line. Each of these corals are iden- by English, et al. (1977:34-51). The method consists tifi ed to species and assigned to one of the following of laying atransect line marked in centimeters along Biodiversity Assessment of Tropical Island Ecosystems Coastal Saltwater Ecosystems 145 seven size classes, based upon the width of their lon- are most critical for management and therefore gest diameters. for monitoring. They are the most important of cor- al-reef resources economically and so they are most 1 indicates 0-5 cm likely to show changes because of human activities. 2 indicates 6-10 cm They also have a key role in maintaining the ecosys- 3 indicates 11-20 cm tem characteristics of coral reefs and therefore their 4 indicates 21-40 cm population densities are of major importance in under- 5 indicates 41-80 cm standing the way in which the ecosystem works and in 6 indicates 81-160 cm predicting future states of the ecosystem. 7 indicates >160 cm Biomass and Size Structure Abundance and living coral cover can be calculated from these data. A common misconception by fi shers is that fi sh are not overharvested when they are seen to still be com- In each of the survey methods for corals mentioned mon. Overharvesting could explain sudden drops in above, corals showing sign of , disease, or fi sh abundance. Fish can be abundant and yet the pop- abnormal growth should be noted, described, and tal- ulation is seriously overfi shed by recruitment overfi sh- lied. ing Right-angle growth-age structure is problematic. Management must be on age, not size. After each quantitative survey, time should be allocat- ed for the coral team to roam the area being surveyed Estimating the size of fi shes in the fi eld is diffi cult and to add species to the list for the area that did not hap- requires substantial training of observers and testing of pen to fall within the quantitative samples. their abilities to estimate the size of fi shes accurately. Methods for training and testing of length estimation Size Distributions and Recruitment in the fi eld are provided by English et al. (1997:93- 97). A main goal of assessing coral reefs is to be able to de- termine the health of the community. “Health” is pri- Scale of Survey marily defi ned as the resilience of the community or the ability to recover from damaging events. Recov- It is important to recognize that fi sh are a diverse group ery is largely the function of recruitment or replenish- of animals that exist over a very broad scale of size ment of the lost individuals in the community. There and range of motility. Any one survey method will be are two general approaches to measuring coral recruit- seriously biased. Therefore, if the entire fi sh is ment: surveying the number of corals recruiting (< 5 being surveyed, several complementary types of sur- cm diameter) to the area, or setting out standard panels vey methods should be used. There are three general of terra cotta, plexiglass, or cleaned carbon- approaches to counting fi shes visually on coral reefs, ate. The standardized methods for settlement plates is the transect, plotless and Manta Tow methods. described by English, et al. (1997). For small (< 20 cm length), site-attached fi shes (e.g., damselfi shes), belt transects 25-m-long and 2-m-wide Fish Communities (50 m2) are used. For larger (20 to 50 cm) and less site- attached fi shes (e.g., snappers), belt transects 50 m Protocol in Coral and Fish Transects long and 3 m wide (150 m2) are used. For large (> 50 cm), motile apex predators such as and jacks, If a team is surveying both the fi sh and the corals, the stationary point counts (300 m2) and 3 km long diver/ coral experts wait in the boat or on shore for 15 to 20 video Manta-Tow surveys are best. A detailed expla- minutes after the fi sh experts enter the water and begin nation of the belt transect method is given on pages 68 their survey. It is best if the coral team waits until the to 80 in English et al. 1997. The Manta-Tow survey fi sh team has completely fi nished the fi rst transect line. method is described by English et al. (1997:14-33). This is because the larger and more motile fi shes will probably be disturbed by divers. Even with this array of survey techniques, more than half of the individuals and over a third of the fi sh spe- Biodiversity Assessment of Tropical Island Ecosystems 146 Coastal Saltwater Ecosystems cies from a locality on a coral reef are cryptic (Green- in the core during extraction of the sample from the fi eld 2003). It is unfortunate that the only known substratum. method for surveying this large portion of the reef community is by using rotenone or other chemicals. The corer should be pushed into the sandy substratum Despite the prevalence of cryptic species (i.e., very at least 50 cm to obtain most of the seagrass small and hidden) in fi sh community structure, they and . The core samples are then dropped into in- are potentially important in the ecological processes dividual plastic buckets. A way of effi ciently transfer- in the reef community and may serve as indicator spe- ring samples from the corer to individual lots for mea- cies of subtle but important processes leading to reef surement is to pour them underwater into fi ne (2 to 4 degradation. mm) prelabeled mesh bags (e.g., laundry bags). In this way, all the samples can be collected underwater and Fish Recruitment carried to the surface on one trip. Also, much of the sediment can be shaken out before removing the sam- The recruitment or replenishment of fi sh stocks is vari- ples from the ocean. able from year to year and the variation in initial re- cruitment and post-recruitment survival is critical to If the samples were placed in a bucket or a bag with- understanding the operations of the coral-reef com- out fi ne mesh, the sediment can be removed by siev- munities. The juveniles of many species of coral-reef ing through a screen of about 2 mm mesh. The sieve fi shes are colorful, and unlike pelagic species stay as- may be constructed of a box about 60 or 40 cm on a sociated with particular sites near the substratum. This side with walls about 10 cm high (exact dimensions makes it feasible to measure year-to-year variation in not critical). After coarse sorting, the fi ne sorting of recruitment and survival of certain species. If fi sh re- small pieces of plant material can be aided by pour- cruitment is found to be defi nitely focused at certain ing the fi ner sieved material into a pan of . times of the year, surveying can be concentrated ap- The live roots and rhizomes tend to fl oat in fresh wa- propriately. The quantitative methods for surveying ter and the dead material tends to sink. Live roots and fi sh recruitment can be found in English et al. (1997: rhizomes tend to be whiter and crisper when squeezed 86-92). while dead material is darker and less crisp. The sorted sample must be all organic matter with no calcium car- bonate fragments. Seagrass Meadows The cleaned samples should be separated fi rst into spe- Abundance cies of seagrass and fl eshy macroalgae. For each sea- grass species, the biomass should be separated into Quadrats (0.25 m2, 25 x 25 cm) are randomly dropped green leaves, non-green leaves, live rhizomes and onto the . For leaves under the quad- roots, and dead rhizomes and roots. Seagrass leaves rat, those from shoots within the quadrat are guided should be cut away from the bundle sheath. Any re- inside and those from shoots outside the quadrat are maining sediment should be removed from the rhi- guided out. the number of shoots within the quadrat zomes and roots by brushing with a soft toothbrush. are counted. on leaves can be removed from seagrass Biomass leaves by soaking in 10% phosphoric or hydrochloric acid. The leaves should stay in the acid until the bub- Biomass measurements are taken with corers. The di- bling stops, but no longer than 10 minutes. The acid ameter of the corer should be about 15 to 20 cm and bath must be replenished regularly because it becomes the length should be about 60 to 80 cm. The cutting ineffective. edge of the corer should be beveled to provide an ef- fective slicing edge. Corers can be made with PVC To remove salt and acid, soak the biomass samples in pipe. The corer needs a handle that extends at least fresh water. Weigh and mark heavy-duty aluminum 20 cm on each side for adequate leverage. The corer foil trays, then place each biomass sample in a tray needs a cap that can be sealed after the corer is in place and dry them at 60 - 90 °C until the weight is constant. so that a vacuum will be formed to keep the material The samples should then be placed in a desiccator to Biodiversity Assessment of Tropical Island Ecosystems Coastal Saltwater Ecosystems 147 cool. Once at room temperature, the biomass samples The daily production of the seagrass per m2 is then can be weighed. calculated by adding all the weights in the new leaves plus growth of marked leaves, the weight is divided by Growth the number of days, and then multiplied by 50 (if the quadrats from which the plants were marked, collect- Relative productivity of seagrass meadows is indi- ed and measured were 200 cm2). The estimates from cated indirectly by measuring the growth of seagrass each quadrat would be considered a sample from that leaves. The water clarity is probably an important fac- seagrass bed for calculating the basic statistics of rela- tor. Light attenuation should be measured with a Sec- tive production to be used in comparison with other chi disk (horizontally) before marking the plants, be- seagrass meadows or with the same seagrass meadow fore collecting the plants, and at the beginning of any at other times. other visit to the area so that light measurements are taken before the diver stirs up the sediment. The rate of turnover can be calculated by adding the previous standing stock to the new leaves plus the To help fi nd the seagrass areas that have been marked, growth of marked leaves for a total standing stock and small quadrats (200 cm2 or 1/50 m2) of the seagrass then dividing the daily production by total standing meadow are outlined with objects in the (per- stock. The estimates from each quadrat can be consid- haps with wire screen or plastic garden border strips). ered a sample for calculating basic statistics on rates of Then all seagrass leaves within the areas are marked turnover. This can be used in comparisons with turn- by punching with a hypodermic needle. The marks over rates in other places and times. should be just above the white-green border of the plant at the base of the leaves. Usually the plant sticks out of the sediment before the white-green border, but Mangrove Stand Communities if not, then mark the plants just where the plant emerg- es from the sand. It is especially important that all the Community Composition plants be marked on the same day. A standard procedure for documenting the structure Marked leaves should be allowed to grow for about and function of mangrove stands is to establish per- 8 to 12 days. For collection, the entire shoot of each manent transect lines perpendicular to the shore, from plant is collected from the sediment and placed in a the highest high water mark to the most seaward man- previously labeled Ziploc bag. In the laboratory, all grove. There should be at least two transects in order leaves on the shoot are clipped at the level at which to have some assessment of variability. The total num- the needle punch mark is found on the oldest leaf. The ber of transects depends on the heterogeneity of the leaves are then separated into three groups: new leaves stand. Five 10 x 10 m (0.01 ha) quadrats are estab- that have emerged since the time of marking, growth lished along each transect line at equidistant intervals. of the marked leaves, and previous standing stock. The fi rst corner is established by marking a tree with The new leaves are green and fresh and have no nee- foresters’ fl agging tape or paint. A compass and a 10 m dle marks. The growth of marked leaves is measured line are used to establish the other corners at the end from the level of the needle punch holes down to the of right angle lines. Stakes, fl agging tape or paint are base. The previous standing stock is the leaf above the used to mark the other corners. needle holes. In each quadrat, all mangrove trees with a diameter The plant material is decalcifi ed in a weak acid and greater than 2.5 cm are numbered with a tag or paint. thoroughly rinsed. Cups of heavy duty aluminum foil The number, position and species of each tree are are numbered and weighed. Each category of plant mapped. Each tree is measured with a diameter tape material is dried on the aluminum foil cup at 60-90 °C at breast height (dbh). For , the diameter until a constant weight is attained, then kept in a desic- is measured right above the buttress roots. It is best to cator until reaching room temperature, then weighed. paint a ring or dash where the measurement of diame- The weight of the aluminum foil is subtracted to ob- ter was taken so it can be taken at exactly the same spot tain the actual dry weight of the plant portion. one year later. If two trunks arise from the same but- tress, each trunk is considered a separate tree. “Drop roots” from high branches are ignored. Biodiversity Assessment of Tropical Island Ecosystems 148 Coastal Saltwater Ecosystems

fruits, , wood and twigs. Each fraction should Height of trees to the top of the canopy can be mea- then be weighed (see Chapter 3). sured with a clinometer. For trees 6 m or less in height, a graduated telescoping rod can be used. As recommended by CARICOMP (1991, the litter traps should be collected monthly during the fi rst year. Recruitment During the following years, only two one-month col- lections need be made, one during maximum and one Within each quadrat, fi ve smaller (1 m2) quadrats during minimum production. should be randomly located. Within each of the fi ve subplots, the rooted seedlings and saplings (< 2.5 cm Plankton Communities dbh) should be identifi ed and tallied. Measurements of community composition and recruitment should be Standardization vis-á-vis Disparate Methods taken once a year, depending on the objectives of the research. Standardization of survey or sampling methods is im- portant when the hypothesis is established and needs Production to be tested, or the important parameters to be moni- tored are chosen with certainty. But if there is a mys- The growth of the individual mangrove trees can be tery or question to be answered, a disparate array of determined from the measurements of community methods is far more helpful than a single method, no composition of one year subtracted from the measure- matter how much more precise that single measure is. ments from the following year. Individual tree weight The historical question of the role of plankton in coral- of living biomass in grams can be estimated by multi- reef ecology is an example of the potential inhibitory plying dbh (cm) x 3,390 (Golley et al. 1962). Total liv- effects of standardization. For a third of a century it ing biomass for each quadrat can be calculated from was a mystery as to how the large biomass of coral- the sum of all the trees in the quadrat and the annual reef communities could maintain a posi- production can be calculated from the sum of the dif- tive energy budget on the meager and quantitatively ferences in living wet weight biomass between years inadequate food supply of plankton drifting in from for each of the trees in the quadrat all added together. the open ocean. This was because the food supply of plankton was defi ned by a standardized method of For rooted seedlings and saplings, the plants with dbh towing nets. When demersal plankton traps, observa- < 2.5 cm can be collected and weighed in some of the tion of mysid swarms next to coral colonies, and other 1 m2 quadrats. The total weights from each of the 1 m2 methods revealed that the majority of the plankton was quadrats can be averaged and the average multiplied resident and would not be caught in a towed or pushed by 100 to add to the estimate of production of plants plankton net, then there was no more mystery. with dbh > 2.5 cm. The multiplication by 100 brings the estimate to a 0.1 ha base. The greatest concentration of biomass around coral reefs are in swarms (Hamner For trees, a lot of the production is shed as litter fall. and Carleton 1979). These would not have been rec- To measure the portion of the production that is shed, ognized by net or by trap. The copepod swarms stay litter fall traps are constructed as baskets from 1 m2 too close to coral colonies or other reef structures to of nylon netting (1.5 mm mesh) attached to a 0.5 x be caught by plankton nets, whether pushed or pulled, 0.5 m wooden or metal frame. The traps should be at- the copepod species that swarm do not enter the sub- tached about 1 m above the substratum: 10 litter fall stratum and large concentrations of the species are traps per quadrat, with 5 parallel to the transect line to not likely to be caught in demersal plankton traps. Al- sample different vegetation zones and 5 perpendicular though these swarms are the greatest single concentra- to the transect line are recommended by CARICOMP tion of coral-reef zooplankton, they have been missed (1991). by standardized zooplankton sampling techniques. They were discovered by divers’ observations. Cope- The traps should be collected and replaced once each pod swarms can be collected by focused pursuit with month. The collection from each trap should be sort- a plankton net pushed by a diver (Emery 1968), with a ed into species and within species to leaves, fl owers, suction device (Emery 1968), or by engulfi ng the wa- Biodiversity Assessment of Tropical Island Ecosystems Coastal Saltwater Ecosystems 149 ter mass with a large plastic bag (Hamner and Carleton and NOAA/CHAMP. Dr. Peters’ website is http://our- 1979). world.compuserve.com/homepages/maccarty_and_ peters/coral/dis-list.htm Any particular sampling program or sampling tech- nique will show only part of the story. The search This website includes color photos of each the disease for latent resources or the search for mechanisms in- in situ on the reef, and a description, cause, distribu- volved in the functioning of the coral-reef ecosystem tion, and impact of each disease for corals, sea fans, should not be restricted to a strictly standardized sam- and crustose . pling procedure. The NOAA/CHAMP Coral Disease Identifi cation and Diseases Information Web Page can be found at http://www. coral.noaa.gov/coral_disease/ Diseases have had a widespread infl uence on the ecol- ogy of coral reefs of the western Atlantic, at least since This site includes identifi cation, verifi cation and a link the mid nineteenth century. The commercial to peer-reviewed literature for each of the coral dis- fi shery in the Florida Keys and Florida areas suf- eases. fered economic setbacks in 1844, 1854, 1878, and 1890 because of heavy losses of sponges through dis- ease. A sponge disease in 1938-39 caused heavy mor- tality of sponges in the Bahamas, throughout the Gulf of Mexico and in British Honduras. The disease on Nutrients are taken up so rapidly by phytoplankton commercial sponges also struck the area in 1947-48. that it is sometimes better to indirectly monitor nutri- ent input by recording when and where phytoplankton In 1983, a disease of the ecologically important sea ur- blooms occur. Concentrations of phytoplankton in the chin Diadema antillarum devastated the populations are indicated by measuring chlorophyll of urchins throughout the western Atlantic, even as far a, b and c. Either a spectrophotometer or a fl uorome- as Bermuda, within the year. By killing over 99% of ter is needed and they are expensive. The methods are the Diadema antillarum, this disease essentially re- given in Parsons, et al. (1984). moved herbivory and for the past 20 years, the mac- roalgae have taken over space from corals (Lessios et al. 1984, Hughes et al. 1985).

In the western Atlantic, the diseases of corals have Acropora palmata have recently been devastated over also reached serious proportions. Serratia marcescens wide areas in the Florida Keys and elsewhere in the Ca- bacteria killed 95% of the elkhorn coral (Acropora ribbean by a bacterial disease (Patterson et al. 2002). palmata) near Key West. The “white pox” disease has Sewage pollution and agricultural runoff often bring been found on corals elsewhere in Florida, in the Ba- bacteria in unusually high concentration. The methods hamas, in the areas of Mexico, and in the for determining bacterial contamination are given in U.S. Virgin Islands (Patterson et al. 2002). Parsons et al. (1984).

Diseases have not reached such large geographic dis- Sampling Considerations tributions in the Pacifi c, probably because of the dis- tances between archipelagoes in the more expansive tropical Pacifi c. Nevertheless, the recording of the Before starting to design your study, remember to presence or absence of diseases should be a part of any make clear exactly the questions you are asking. Do coral-reef survey program. It will probably be valu- not just measure any variables that come to mind in able in the future to have baseline data on coral dis- hopes that some will provide new insights and useful eases in the Pacifi c now, before diseases become more information. Identify the factors you perceive as im- prevalent. portant to understanding the causes. Explain your ob- jectives to others. If they cannot quite see the worth of The two best sources of up-to-date information on dis- your study, then the objectives need to be more clearly eases can be found on the websites of Dr. Esther Peters defi ned. Which methods are better and the scales in- Biodiversity Assessment of Tropical Island Ecosystems 150 Coastal Saltwater Ecosystems volved in the design depend on the questions being means more ability to determine and show a real dif- asked. ference between two populations.) A nested sampling design is having replicate samples within each scale If you are only interested in one reef and the monitor- of sampling. For example, within each of several reefs ing program involves intensive sampling on one reef, sampled in the region, there would be several transects you may have a reliable estimate of the variation in on each reef, and within each transect there would be space and time on this one reef. However, the conclu- several quadrats. This would allow a measure of varia- sions may not be generalizable to other reefs in the re- tion among reefs, within reefs, and within transects. gion. For example, if you wish to monitor the yearly We can only generalize for reefs in the region of we variation in coral recruitment to learn how dependable are able to quantify the variance among reefs. recruitment is, you could count the recruits in 30 or so quadrats spread across the reef each November. This It is important to decide what aspects of the reef may could give a good estimate of variation in recruitment be important. If we were examining the yearly vari- to this particular reef. But other reefs have different ation of coral recruitment, we may want to know if current patterns, different characteristics of adjacent there is more recruitment above 10 m depth than be- land, different proximity to mouths, different low, or more recruitment on the leeward side than on wave exposures and so forth. The 30 samples of coral the windward. To determine the answers to these ques- recruitment to one reef would provide little informa- tions, we would need to stratify our sampling. Rather tion about any other reef. It is important to spread your than distributing the samples randomly over the entire sampling effort across the region for which you wish reef, we distribute them randomly in equal portions to draw broader conclusions. below 10 m and above 10m depth or on the leeward and on the windward sides of the reefs. At the opposite direction of scale, if all the samples were in one zone or section of the reef, you could not Monitoring requires repeating surveys over time. safely generalize about the reef as a whole because These can be done in two ways: returning to the ex- the wave exposure, characteristics of topography and act same permanently marked site, or taking random depth vary on each reef. The samples would only pro- samples from the same close proximity. There are ad- vide information on the nature of the variation on the vantages and disadvantages to both. one zone or section of the reef and so it would be mis- leading to generalize to the whole reef. If ten samples Permanent Quadrats and Photographic Records were taken along one transect, it would be one repli- cate statistically, not ten, if the goal was to generalize The data from permanent quadrats are almost always beyond the section of reef being surveyed. To consider recorded in the fi eld through photography. This gives ten samples on one transect as ten replicates for sta- especially useful insights into biological processes tistical analysis would be pseudoreplication (Hurlbert such as growth, disease, for space, mor- 1984) unless the study was not intended to be general- tality, and recruitment because individual colonies are ized beyond the one transect. Two transects with ten followed through time. Data from random quadrats or samples each would be two replicates. transects are most often recorded directly as data writ- ten with pencil, although random transects have re- If we were actually interested in the yearly variation cently become more frequently recorded by video. of coral recruitment to reefs in the region as a whole, then we should spread our samples across a random Whether permanent or random, many aspects of the selection of reefs throughout the region. If we did this site that may not have been in the initial question are by having one transect or one sample per reef, then a in the photographic record and so the photographs can great part of the variation in recruitment may actually be reexamined if new questions arise, perhaps years be hidden within each reef rather than between reefs as later. Another bonus is that photographs can provide we would be likely to conclude. It is necessary to have material for communicating the results to the public. at least two replicates per reef when we are sampling Photographs and video are more effective media than over several reefs in the region to get an estimate of are graphs when communicating with the public. Dis- the variance within reefs as well as between reefs. The advantages of photography are that identifi cation of most powerful way to accomplish this is with a nest- corals and other organisms to the species level is of- ed sampling design. (Statistically, more “powerful” ten not certain, shading and rugosity of the area pho- Biodiversity Assessment of Tropical Island Ecosystems Coastal Saltwater Ecosystems 151 tographed make it questionable that the photographs the standard error of the mean (the standard deviation will provide a clear image of the area, and the analysis of the statistical mean that is estimating the parameter, can fall years behind the collecting of data. Many pho- or true mean) is the natural standard deviation divid- tographs can be taken in a single day, but the analysis ed by the square of the sample size. With more of the images may take months or years. data, the estimate of the mean will become more pre- cise. The degree of certainty is obtained by using the The most time-consuming aspect of fi eldwork is relo- t-value for differentiating a single estimate from a true cating permanent quadrats or transects. Modern GPS value or by using the F-value for distinguishing among equipment makes it easier than in past years, but to zones, populations, times etc. Easily used tables for fi nd the stakes or nails is still diffi cult. It is important power analyses, i.e., determining sample sizes neces- to diagram the natural physical features of the area so sary to achieve given degrees of certainty and preci- the location of the permanent quadrats can be mapped. sion for populations of given variances relative to the Permanent quadrats must be located by permanent precision desired, can be found in Norman and Strein- stakes, preferably at four corners. Rogers et al. (1994) er (1994). A simple fi eld method is “plotting the run- present the most thorough explanation of photographic ning mean” (see Chapter 3). data acquisition. English et al. (1997: 52-67) describe the procedures for establishing and monitoring perma- Another reason for obtaining preliminary data is to be nent quadrats. Both references describe and illustrate sure the methods work before you commit too much to the procedure of rigging an underwater camera on a the sampling design. It is a mess if you start off with a frame over the permanent quadrats. monitoring program for a couple of years and then de- cide to change to better methods found later. Random Sampling A monitoring, sampling or experimental program has Random sampling may require more samples to sta- several levels and sublevels, e.g., treatments, sites, tistically detect the same amount of change. However, times, zones, transects and so forth. The power and the changes recorded by numerous random samples effi ciency of these programs can be assessed with a may be more representative of the area you wish to cost-benefi t analysis. The goal is to reduce the vari- understand. ance by the greatest amount at the least expense. The relative expense of each subsection of the program can Effi cient Program Design be evaluated in terms of time and money by assign- ing a dollar value to the time and estimating the cost It is important to determine the number of replicates of travel, boat-use and any such use of personnel and and samples required to obtain results accurate enough materials. for the conclusions with the degree of confi dence you need. Otherwise you may put in a lot of time and effort The statistical power of the sampling program de- and be left with inconclusive results. It is critical to pends on the relative magnitude of variation at each determine whether the variables measured are signifi - level. The most certain information is obtained when cantly different among times and sites. In order to re- the variance is reduced the most. Therefore, the most solve the number of replicates and samples needed to replicates should be at the level with the greatest vari- accomplish this, you fi rst need some preliminary data ance. Generally, the variance is greatest at the upper (Green 1979). From these few preliminary data you levels so this is where the samples should be replicated can calculate a standard deviation and from this stan- the most, but the cost is also generally greatest at the dard deviation you can determine the number of sam- upper levels and so this is where the samples should ples necessary to obtain an estimate of the true val- be replicated the least. This creates a dilemma, but the ue within any degree of accuracy with any degree of logically optimal solution to this is solved by the fol- certainty (Norman and Streiner 1994, Sokal and Rohlf lowing calculations. The most effi cient number of rep- 1995). Basically, the uncertainty in your fi ndings will licates at the lower level of subgroups (n) is be the width of the natural standard deviation of the population you are studying. The standard deviation (S2 @ lowest level)•(Cost @ next higher level) of the population should not change substantially with n = ——————————————————— more data, but the estimation of a parameter such as a (S2 @ next higher level b)•(Cost @ lowest level) mean will become narrower with more data because Biodiversity Assessment of Tropical Island Ecosystems 152 Coastal Saltwater Ecosystems where S2 is the sample variance. monitoring is to determine if variables are truly dif- ferent among sites and between survey periods. The To calculate the number of replicates at the next higher following measurement procedures are used by the level (nb), we take CARICOMP (Caribbean Coastal Marine Productiv- ity) program (CARICOMP 1991). CARICOMP is a (S2 @ level b)•(Cost @ still higher level) cooperative program among 25 laboratories in the Ca- nb = —————————————————— ribbean to study the productivity, structure and func- (S2 @ still higher level)•(Cost of level b) tion of mangroves, seagrass meadows and coral reefs. CARICOMP began over two decades ago so it is rec- This process could be continued up through as many ommended that the CARICOMP protocol be followed levels as necessary, but, of course, the expense in time to allow comparisons between . These CARI- and effort goes up geometrically as levels are added COMP methods are all very simple and can be done and so the limit of possible additional levels approach- without technologically advanced methods. es rapidly. Temperature For the power of a survey, the ability to obtain the most conclusive results for the fewest data, the best strategy Water temperatures are taken by holding the thermom- is to focus effort on the highest level of sampling. If eter 0.5 m (to your elbow) below the surface for 2 min- effort or sampling is limited, sacrifi ce samples at the utes to allow time for the thermometer to equilibrate. lower levels in favor of retaining replicates at the high- Air temperatures are taken 1.5 m above the ground, est levels to the extent that is economically feasible always shaded from the sun. Max/Min thermometers (Sokal and Rohlf 1995: 317). should be secured in locations where they are never in the direct . Air temperatures should be record- Field Sampling Needs Follow-Up Work ed to the nearest 0.1 °C.

Collecting specimens from the fi eld may be possibly diffi cult and strenuous, but it is nearly always sever- al times more rapid than the subsequent work need- Place a container with a lid 0.5 m (elbow length) be- ed. Specimens for taxonomic identifi cation, or neath the surface, open the container, let it fi ll with coral colony cores for growth-ring analysis, or video- water, then close the lid and bring it to the surface. tapes of transects all require a substantial investment Put a few drops of water on the measurement plate of of time subsequent to fi eld work. In designing a proj- a refractometer and record salinity to the nearest part ect, the grant proposal and planning should give as per thousand. much or even more emphasis for the analysis of speci- mens, videotapes, growth rings and other materials af- Rainfall ter the fi eld work as to the fi eld work itself. Videotapes do not last indefi nitely, even under the best provisions Secure the rain gauge 1.5 m above ground in an open of air conditioning; CDs or DVDs are better. The con- area at least 25 m from any obstacles. Record to the tents of bottles of taxonomic specimens and stomach nearest millimeter the rainfall that has accumulated contents can become desiccated over time. As the bio- during the past 24 hours, then empty the gauge. logical specimens and video recordings languish over time, they may deteriorate and be forgotten. It is im- perative that follow-up work is given as much or more emphasis in grant proposals and program planning as Lower a 0.3 m Secchi disk until it can no longer be is the fi eld work. seen from the surface. Record the depth to 0.1 m. The sun must be overhead so Secchi disk readings must be made between 1000 and 1400. Physical Parameters In seagrass meadows, the water is too shallow to take For monitoring, physical parameters should be tak- vertical Secchi disk readings so they must be tak- en in a consistent way throughout the study to make en horizontally. Have a partner hold the Secchi disk comparisons valid among times and sites. The goal of vertically 0.5 m underwater and also hold the end of Biodiversity Assessment of Tropical Island Ecosystems Coastal Saltwater Ecosystems 153 the measuring tape (perhaps a transect tape). Swim or phates, silicates, iron) take especially clean glassware wade away from the disk, drawing the measuring tape, and a well-equipped chemical laboratory. The meth- until you can no longer see the disk underwater with ods are presented in Strickland and Parsons (1972) and a face mask. in Parsons et al. (1984), but they are diffi cult. Because phytoplankton and bacteria rapidly take up nutrients, Sedimentation samples should usually be cooled right away and fi xa- tives should usually be added right away in order to Increase in sedimentation because of inappropriate stop any biological activity that will change the sam- land management is one of the major factors caus- ple as it is being taken to the laboratory. ing deterioration of coral-reef ecosystems (Johannes 1975). Therefore, documentation of the increase in Special Considerations rates of sediment deposition is especially important. Sediment deposition is usually measured by placing Context of Diversity cylinders with open tops about 20 cm above the sub- stratum. Sediment settles into these traps over about a In the tropical Pacifi c, care should be taken if thinking two-week period. the cylinders are sealed and trans- of using diversity of species, higher taxa or habitats as ported to the laboratory where the sediment is dried an indication of or stress. Habitats such and weighed. as mangrove stands, classes of organisms such as the Crinoidea, and numbers of species naturally drop con- These cylindrical sediment traps are described in Rog- siderably from west to east across the tropical Pacifi c. ers et al. (1994: II-8) and English et al. (1997: 56). This is mainly because of the Coriolis Effect and the Gardner (1980) determined that the depth should be resultant main currents from east to west. A drop in di- about two to three times the width of these cylinders. versity over time in any one location may be an indica- If the cylinders are too narrow (small opening) the wa- tion of damaging factors, but a difference in diversity ter resists sediment entering the cylinder. If the cyl- between areas does not necessarily indicate detrimen- inder is too wide relative to depth (like a pan or dish) tal forces. the sediment might be washed back out of the trap by water motion. If the water motion is greater than 15 For example, Palmyra Atoll was not settled by Poly- cm per second, the height should perhaps be even tall- nesians and by all indications the fi shes and corals are er in proportion to the width. Blennies (small fi shes) in nearly pristine condition. Guam, in contrast, was the frequently take up residence in one of a set of tubes fi rst island landed by Magellan and has been exploit- and invalidate the sample. Baffl es or screens at the top ed by Europeans and Americans since 1521. The fi sh opening of the sediment tubes are helpful in prevent- stocks on Guam are about a quarter of what they were ing animals taking up residence and may also help in before the mid-1980s (Birkeland 1997). Yet Guam has inhibiting resuspension of the sample. about six species of crinoids and Palmyra probably has none. Guam has 24 species of asteroids, Palmyra prob- Inorganic Chemicals in the Water Column ably has about eight. Guam has 267 species of scler- actinian corals, while170 species have been found on Nutrients are very important in coastal marine ecosys- Palmyra and there are probably not more than 200. tems. Millions of die and fi sheries collapse Guam has been severely stressed for nearly 500 years during El Niño years because the of nutri- and the outer reef slopes of Palmyra have been left ents cease and the food-web deteriorates from the bot- alone, yet Guam will always have a far greater species tom. Eutrophication, the input of extra nutrients, into richness than Palmyra. A change in diversity through coastal areas is a serious form of pollution by human time at one site can be indicative of stress from human activities and can cause red , increase in paralyt- activities, but a comparison of diversity between areas ic shellfi sh poisoning, algal blooms, and outbreaks of is confounded by longitude, continents vs. oceanic is- crown-of-thorns starfi sh. Therefore, nutrients are an lands, high islands vs. atolls, and the location of natu- especially important component of the physical envi- ral forces such as large rivers. ronment to monitor.

Unfortunately, chemical analysis of water samples for inorganic nutrients (, nitrites, , phos- Biodiversity Assessment of Tropical Island Ecosystems 154 Coastal Saltwater Ecosystems

Caveat—“Sliding Baseline”: Need young scientists to conclude that the high islands have to Deduce Past History more herbivorous fi shes than the Northwestern Ha- waiian Islands because of greater productivity on the Changes in the habitats of the coastal regions are pro- high islands. In truth, there is still a substantially great- ceeding very rapidly, almost always as degradation. As er biomass of herbivorous fi shes in the Northwestern human populations grow, a greater portion of the pop- Hawaiian Islands, despite the herbivorous fi shes be- ulations become concentrated in the coastal regions. ing a considerably smaller component of the reef fi sh Land is cleared for urbanization, harbors are altered biomass. On Guam, the less desirable fi shes dominate to accommodate shipping facilities, and coastal veg- the reef fi sh fauna in the accessible reefs and it could etation is replaced with buildings and roads. To have be mistakenly assumed that nemipterids are preva- any responsible management, it is necessary to docu- lent over lutjanids on the more accessible reef fl ats of ment the changes that are occurring now. The data that Guam (Katnik 1982). are collected by the methods in this book can provide “baseline” data sets and document changes from future Socioeconomics human activities, global climate changes, and natural events such as effects of cyclones, fl ows, crown- Of course it is unrealistic to consider coastal ecosys- of-thorns outbreaks, and so forth. However, it is im- tems in which human activities are not affecting the portant to recognize that these changes are probably system. In monitoring the coastal ecosystems with measured from an artifi cial “baseline” that has been the objectives of sustainable management, we must shifting for decades and is substantially different than know the perceptions of the reef resources by the local what would be considered natural. In order to make ra- people, their livelihoods, technical means for fi shing tional decisions as to the proper action to take in habi- and processing, traditional and modern jurisdictional tat restoration or protection, we should have a realistic boundaries, and many socioeconomic factors. These perception as to the true “baseline” for the area. There are just as important as the aspects already discussed are several things to consider when trying to recon- in this chapter, but they require a whole book in them- struct a true “baseline”. selves. Such a book is the “Socioeconomic Manual for Coral Reef Management” by Bunce et al. (2000). This The “baseline” fi sh populations in American Samoa, manual is available from Science Communication, Guam, and the main Hawaiian Islands are probably Australian Institute of Marine Science, P.M.B. No. 3, about 20% of their natural levels of abundance and bio- Townsville M.C., Townsville Qld 4810, . mass (Shomura 1987, Clark and Gulko 1999, Birke- land and Friedlander 2002, Friedlander and DeMar- tini 2002). Communication with the public is impor- Literature Cited tant. When communicating to the public, it would be irresponsible not to make clear that the “baseline” of Birkeland, C. 1997. Status of coral reefs in the Mari- today is a small percentage of what would be the ex- anas.Pages 91–100 in: R.W. Grigg and C. Birkeland pected baseline under normal circumstances without a (eds.) Status of coral reefs in the Pacifi c. University of previous history of . Hawaii Sea Grant College Program, Honolulu. 144 p.

Likewise, faunistic surveys should recognize the need Birkeland, C. 1985. Ecological interactions between for detective work to determine whether the species mangroves, seagrass beds and coral reefs. Pages 1-26 were endemic or introduced on the hulls of wooden in: Ecological interactions between tropical coastal centuries ago. This especially applies to the cir- ecosystems. UNEP Regional Reports and Stud- cumtropical or especially wide-ranging species of al- ies No. 73. 65 p. gae, sponges, bryozoans and ascidians. have sometimes been predominant species in Birkeland, C. and J. S. Lucas. 1990. Acanthaster plan- tropical Pacifi c ecosystems (e.g., Lutjanus kasmira, L. ci: major management problem of coral reefs. CRC fulva, and Cephalopholus argus in the coral reefs of Press, Boca Raton. 257 p. the Hawaiian Islands) and younger generations for- get they were not indigenous. The overharvest of apex Birkeland, C., and A. M. Friedlander. 2002. The im- predators and the resultant predominance of herbiv- portance of refuges to reef fi sh replenishment in Ha- orous fi shes in the Main Hawaiian Islands may lead waii. Hawaii Audubon Society, Honolulu. 19 p. Biodiversity Assessment of Tropical Island Ecosystems Coastal Saltwater Ecosystems 155

Bunce, L., P. Townsley, R. Pomeroy and R. Pollnac. Hatcher, B. G. 1997. Organic production and decom- 2000. Socioeconomic manual for coral reef manage- position. Pages 140-174 in: C. Birkeland (ed.) Life ment. Austr. Inst. Mar. Sci., Townsville. 251 p. and death of coral reefs. Chapman & Hall, New York. 536 p. CARICOMP (Caribbean Coastal Marine Productivi- ty): Manual of methods for mapping and monitoring of Hughes, T. P., B. D. Keller, J. B. C. Jackson, and M. physical and biological parameters in the coastal zone J. Boyle. 1985. Mass mortality of the echinoid Diade- of the Caribbean. 1991. Florida Institute of Oceanog- ma antillarum Philippi in Jamaica. Bull. Mar. Sci. 36: raphy, St. Petersburg, Florida. 35 p. 377-384.

Clark, A. M., and D. Gulko. 1999. Hawaii’s state of Hurlbert, S. H. 1984. Pseudoreplication and the design the reefs report. 1998. State of Hawaii, Department of of ecological fi eld experiments. Ecological Mono- Land and Natural Resources, Honolulu. 41 p. graphs 54: 187-211

Emery, A. R. 1968. Preliminary observations on coral Johannes, R. E. 1975. Pollution and degradation of reef plankton. Limnol. Oceanogr. 13: 293-303. coral reef communities. Pages 13-51 in: E.J. Ferguson Wood and R.E. Johannes (eds.), Tropical marine pol- English, S., C. Wilkinson and V. Baker (eds.) 1997. lution. Elsevier Oceanogr. Ser. 12. Elsevier, Amster- Survey manual for tropical marine resources (2nd edi- dam. 192 p. tion). Australian Institute of Marine Science, Towns- ville. 390 p. Katnik, S. E. 1982. Effects of fi shing on the reef fl at fi sheries of Guam. Master’s thesis, University Friedlander, A. M., and E. DeMartini. 2002. Contrasts of Guam Marine Laboratory. 62 p. in density, size, and biomass of reef fi shes between the Northwestern and main Hawaiian Islands: effect Kirkman, H., and D. D. Reid. 1979. A study of the role of fi shing down apex predators. Mar Ecol. Progr. Ser. of a seagrass australis in the carbon budget 230: 253-264. of an . Aquat. Bot. 7: 173-183.

Gardner, W. D. 1980. Field assessment of sediment Lessios, H. A., D. R. Robertson, and J. D. Cubit. 1984. traps. J. Mar. Res. 38: 41-52 Spread of Diadema mass mortality through the Carib- bean. Science 226: 335-337. Golley, F., H. T. Odum and R. F. Wilson. 1962. The structure and of a Puerto Rican red man- Norman, G. R. and D. L. Streiner. 1994. Biostatistics: grove forest in May. Ecology 43: 9-19. The Bare Essentials. Mosby, Chicago. 260 p.

Green, R. H. 1979. Sampling design and statistical Ogden, J. C. 1997. Ecosystem interactions in the tropi- methods for environmental biologists. Wiley, New cal coastal seascaape. Pages 288-297 in: C. Birkeland York. 257 p. (ed.) Life and death of coral reefs. Chapman & Hall, New York. 536 p. Greenfi eld, D. W. 2003. Pacifi c-Atlantic differences in cardinalfi sh assemblage structure. Copeia 200: 608- Parsons, T. R., Y. Maita, and C. M. Lalli. 1984. A Man- 617. ual of Chemical and Biological Methods of Analysis. Pergamon Press, New York. 173 p. Hamner, W. M. and J. H. Carleton. 1979. Copepod swarms: attributes and role in coral reef ecosystems. Patterson, K. L., J. W. Porter, K. B. Ritchie, S. W. Pol- Limnol. Oceanogr. 24: 1-14 son, E. Mueller, E. C. Peters, D. L. Santavy, and G. W. Smith. 2002. The etiology of white pox, a lethal Harrison, P. G., and K. H. Mann. 1975. Detritus for- disease of the Caribbean elkhorn coral Acropora pal- mation from eelgrass ( marina L.): the relative mate. Proc. Nat. Acad. Sci. 99: 8725-8730. effects of fragmentation, leaching, and decay. Limnol. Oceanogr. 20: 924-934. Biodiversity Assessment of Tropical Island Ecosystems 156 Coastal Saltwater Ecosystems

Randall, R. H., and C. Birkeland. 1978. Guam’s reefs This manual covers methods for measuring and : Part II: Sedimentation studies at Fouha the physical environment as well as survey- Bay and Ylig Bay. University of Guam Marine labora- ing communities of fi shes, corals, inverte- tory Technical Report No. 47. 77 p. brates, plants and algae. The methods for surveying coral reefs, mangrove ecosystems, Rogers, C. S., G. Garrison, R. Grober, Z.-M. Hillis and soft-bottom communities, seagrass commu- M. A. Franke. 1994. Coral Reef Monitoring Manual nities, coastal fi sheries are all covered. There for the Caribbean and Western Atlantic. National Park are special sections on planning of sampling Service, Virgin Islands National Park, St. John, US design and monitoring programs, as well as Virgin Islands. 112 p. database design and operation.

Shomura, R. S. 1987. Hawaii’s marine fi shery resourc- Dartnall, A. J. and M. Jones (eds.), 1986. A Manual of es: yesterday (1900) and today (1986). Southwest Fish- Survey Methods: Living Resources in Coastal Areas. eries Center Administrative Report H-87-21. 15 p. AIMS, Townsville.

Sokal, R. R. and F.J. Rohlf. 1995. Biometry. W.H. CARICOMP (Caribbean Coastal Marine Produc- Freeman, New York. 887 p. tivity). 1991. Manual of methods for mapping and monitoring of physical and biological parameters in Spalding, M.D., F. Blasco, and C. D. Field (eds.) 1997. the coastal zone of the Caribbean. Florida Institute of World mangrove atlas. The International Society for , St. Petersburg, Florida. 35 p. Mangrove Ecosystems. Okinawa, Japan. 178 p. This manual covers the measurements of Strickland, J. D. H. and T. R. Parsons. 1972. A Prac- physical and biological parameters for coral tical Handbook of Seawater Analysis. Re- reefs, mangrove stands and seagrass mead- search Board of Canada, Ontario, Canada. ows. The methods covered in this manual are all low expense, low technology. UNESCO. 1984. Comparing Coral Reef Survey Meth- ods. 1984. Report of a regional UNESCO/UNEP The UNESCO Monographs on Oceanographic Tech- Workshop, Phuket Marine Biological Centre, Thai- nology has each habitat in a separate hard-cover vol- land. UNESCO Report in Marine Science No. 21. 170 ume. p. Stoddart, D. R. and R. E. Johannes (eds.), 1978. Coral Wilkinson, C. R. (ed.) 1994. Living coastal resources Reefs: Research Methods. UNESCO, Paris. 581 p. of Southeast Asia: status and management. Report of the Consultative Forum on Living Coastal Resourc- This manual is divided into three sections es, Australian Agency for International Development. which cover research methods in coral reef 133 p. morphology and structure, biotic distribu- tions, and energy and nutrient fl ux through Appendix — Manuals for coral reef communities. Field Survey Techniques Snedaker, S. C. and J. G. Snedaker (eds.), 1984. The Mangrove Ecosystem: Research Methods. UNESCO, Manuals for fi eld techniques are available for coral Paris. 251 p. reef, mangrove and seagrass studies. Here is a list of some of the more useful manuals. This manual is divided into three sections which cover characterization of the man- Manuals for all Three Habitats grove environment, community structure and description, and mangrove functions and English, S., C. Wilkinson and V. Baker (eds.), 1997. community processes. Survey Manual for Tropical Marine Resources. Aus- tralian Institute of Marine Science, Townsville. 390 p. Phillips, R. C. and C. P. McRoy (eds.), 1990. Seagrass Research Methods. UNESCO, Paris. 210 p. Biodiversity Assessment of Tropical Island Ecosystems Coastal Saltwater Ecosystems 157

Manuals for Mangrove Research Methods The three sections of this manual deal with seagrasses, associated biota, and ecosystem Ong, J. E., W. K. Gong, C. H. Wong, and Z. B. H. measurements. Din. 1985. Productivity of the Mangrove Ecosystem: A Manual of Methods. Penang, Malaysia. 117 p. Manuals for Coral Reef Research Methods Kjerfve, B. Manual for Investigation of Hydrologi- All of these handbooks describe techniques for sur- cal Processes in Mangrove Ecosystems. UNESCO/ veying or counting corals, fi shes, and other coral-reef UNDP. 79 p. biota. Field, C. D. and A. J. Dartnall (eds.), 1987. Mangrove Coral Reef Monitoring Manual for the Caribbean and Ecosystems of Asia and the Pacifi c: Status, Exploita- Western Atlantic. C. S. Rogers, G. Garrison, R. Grob- tion and Management. AIMS, Townsville. 321 p. er, Z. M. Hillis, and M. A. Franke. 1994. National Park Service, Virgin Islands National Park, St. John, US Snedaker, S. C. and A. E. Lugo. 1973. The Role of Virgin Islands. 112 p. Mangrove Ecosystems in the Maintenance of Envi- ronmental Quality and a High Productivity of Desir- Pernetta, J. C. (comp.), 1993. Monitoring Coral Reefs able Fisheries. Bureau of Sport Fisheries and Wildlife, for Global Change: A and De- Gainesville. 404 p. velopment Report.IUCN, Gland, Switzerland. 74 p. Manuals for Seagrass Research Methods

Monitoring Coral Reefs for Global Change: Reference Phillips, R. C. and C. P. McRoy (eds.), 1980. Hand- Methods for Studies No. 61. 1993. book of Seagrass Biology: An Ecosystem Perspective. UNEP/AIMS, Paris. 72 p. Garland Publishing, New York. 353 p.

Comparing Coral Reef Survey Methods. 1984. Report Manuals for Assessing Water Chemistry of a regional UNESCO/UNEP Workshop, Phuket Ma- rine Biological Centre, Thailand. UNESCO Report in Strickland, J. D. H. and T. R. Parsons. 1972. A Prac- Marine Science No. 21. 170 p. tical Handbook of Seawater Analysis. Fisheries Re- search Board of Canada, Ontario, Canada. Dahl, A. L. 1981. Coral Reef Monitoring Handbook. South Pacifi c Commission Publications Bureau, Parsons, T. R., Y. Maita and C. M. Lalli. 1984. A Man- Noumea, New Caledonia. 21 p. ual of Chemical and Biological Methods of Seawater Analysis. Pergamon Press, New York. 173 p. Coral Reef Monitoring Handbook. Reference Meth- ods for Marine Pollution Sudies No. 25. 1984. UNEP, Manuals for Assessing Geneva. 25 p. Samoilys, M. (ed.). 1997. Manual for Assessing Fish McManus, J. W., M. C. A. Ablan, S. G. Vergara, B. Stocks on Pacifi c Coral Reefs. Department of Primary M. Vallejo, L. A. B. Meñez, K. P. K. Reyes, M. L. G. Industries, Brisbane, Australia. 78 p. Gorospe and L. Halmarick. 1997. ReefBase Aquanaut Survey Manual. ICLARM Educ. Ser. 18, Manila. 61 p.

Kenchington, R. A. and B. Hudson (eds.), 1984. Cor- al Reef Management Handbook. Regional Offi ce for Science and Technology for Southeast Asia. 281 p. Biodiversity Assessment of Tropical Island Ecosystems 158 Coastal Saltwater Ecosystems