marine atlas of the western arabian gulf - saudi … · 116 marine atlas of the western arabian...

116 M a r i n e A t l a s o f t h e W e s t e r n A r a b i a n G u l f

Plate 5.1 Diver highlights fish on a coral reef.

CHAPTER 5__PART1_FINAL_10MAY2011_jpk_VERONA.indd 116 17/07/12 23:02

Charles Sheppard

Warwick University UK

Michael Borowitzka

Murdoch University, Western Australia


118 119C h a p t e r 5 : S U B T I D A L H A B I T A T SM a r i n e A t l a s o f t h e W e s t e r n A r a b i a n G u l f

Introduction

The life on the surface of the seabed along the coasts of Saudi Arabia almost certainly comprises Saudi Arabia’s greatest biodiversity.

While the Gulf Coast is not particularly diverse in global terms, its greater environmental extremes cause greater physical stresses than almost any other sea area in the world, which has led to several remarkable examples of environmental adaptation. This, in turn, has led to several important discoveries about how life lives under stress. More than the pelagic zone, the seabed supports the greatest productivity too, so the thin layer of life on the seabed is the heart of the marine biology of the Gulf.

Most people’s attention is usually drawn to the important components of coral reefs, rich seagrass and algae beds. However, these are not the only important benthic habitats. Regarding hard substrates, two major groupings may be made: hardgrounds and coral reefs. Even combined these are relatively small in area, but these together support the greater biodiversity. The hardgrounds are an unusual feature of the Gulf. Sometimes called shoals, they are limestone expanses, often covered with a film of shifting sand, with too few corals for them to be commonly regarded as true reefs but sometimes supporting substantial quantities of attached algae and fauna. In contrast to the hardgrounds and reefs, the largest proportion of seabed by far in terms of area is composed of soft, muddy or sandy substrate. While not as biodiverse, and commonly overlooked as being relatively unimportant, most of the secondary and much of the primary productivity of the Gulf comes from these soft substrates. Some soft substrate components, such as seagrass and algal beds are well researched and are very strongly photosynthetic, contributing in a major way to primary productivity. But other parts which lie in water too deep for primary production also contribute hugely to secondary productivity, and such sites may validly be thought to drive much of the marine ecology of the region.

Plate 5.2 Soft coral (Goniopora djiboutensis) traps zooplankton from the water.

Plate 5.4 Box fish (Ostracion sp.), Family Ostraciidae. Plate 5.3 Diver filming turtle on coral reef.


SeagrassSeagrasses are rooted plants attached in soft substrates. Some may grow in surprisingly thin films of soft substrate overlying rock, but mostly they are found in shallow bays of fine sand. Their most visible components are of course their carpets of leaves above ground where they form a characteristic habitat, which supports large numbers of other species. However, they also have an equally large biomass below the surface where their substantial root networks have great importance in stabilizing substrate, which otherwise would be mobile and possibly erosional. Large stands of seagrass resemble underwater fields but, equally commonly, seagrass beds can be sparse and scattered, though even here their roots may provide important stabilizing control on the potentially mobile and shifting substrates.

Seagrasses are flowering plants, and are the only group of flowering plants able to withstand permanent submergence in seawater (unlike freshwater where very many different plants may live). They belong to two families in one single order of Monocotyledons. Despite their name they are not true grasses but are more closely related to freshwater pond weeds. The term seagrass therefore has ecological validity if not a taxonomic one.

Fifty species of seagrasses belonging to 12 genera are known from around the world. Eleven species have been recorded from the whole Arabian region (Sheppard, et al., 1992), four of which are known from the Western Arabian Gulf: Halophila stipulacea (Plate 5.5) and Halophila ovalis (Plate 5.6) are widespread; Halodule uninervis (Plate 5.11) however, is probably the most common species (Phillips, 2003; Price, et al., 1987b; Price and Coles, 1992; Richmond, 1996). The fourth species, Syringodium isoetifoleum was reported to occur in Abu Ali Bay (KFUPM/RI, 1988). Although not verified, S. isoetifoleum probably occurs in Tarut Bay as well.

Plate 5.5 Seagrass, Halophila stipulacea.

Definition of a seagrass ecosystem has problems in many areas of the Gulf because they so commonly occur with other habitat types. In sheltered bays in particular, where substrate is a mixture of coarse sand and rubble, perhaps with dead coral fragments and rocky outcrops, seagrasses often grow in a mixed community with algae, being sometimes less common than seaweeds and sometimes more so. Huge areas, especially in sheltered embayments, may contain these mixtures. Seagrasses, whether mixed with algae or not, also grow in sheltered sandy pockets among coral reefs. Here, seagrass ecosystems are taken to include those where seagrasses are the dominant group.

Although seagrass beds are visually more uniform and usually less spectacular than coral reefs, their ecological significance is probably comparable in terms of productivity, even more so given that the area they cover is far greater in the Gulf than the area covered by reefs. Their importance as primary producers in these coastal environments has been known for more than 100 years. Their gross productivity may rival even intensively cultivated tropical agriculture systems. Because of this, their inclusion in the category which is commonly called “critical marine habitats” is fully justified, and their high primary productivity means they can fairly be regarded as being coastal food factories. Often their productivity is made even greater by encrusting algae that attach onto the seagrass blades, and by epiphytic cyanophytes which also fix nitrogen.

However, seagrass blades are, perhaps surprisingly, not particularly edible to most herbivores and are eaten directly only by relatively few of the species which depend on them. Examples include some urchins, several fish, and most spectacularly green turtles and dugong. But while these feed on them directly, the main basis for their productivity is mediated through the


121C h a p t e r 5 : S U B T I D A L H A B I T A T S

Plate 5.6 Seagrass, Halophila ovalis.

Plate 5.7 Goby fish (Microgobius gulosus) live in symbiosis with shrimp.

Plate 5.8 Starfish live among the benthos.

microbial food web. In this, breakdown and decay of leaves mostly takes place through the action of complex microbial pathways in which microbial organisms, especially bacteria, breakdown the dead or dying leaves, following which the accumulations of microbial growth become the basis of food chains for small grazing or browsing organisms, which themselves then become food for larger organisms. Much less is known about the mechanisms, species and rates of turnover of the microbial food chain than is known about the more spectacular and visible components, yet the microbial loop, as it is known, is undoubtedly the most important component in quantitative terms.

Seagrass leaf biomass turnover may be 1% to 2% of the total biomass per day, much of this turnover being mediated via the microbial loop. Standing crop may be as much as 0.25 kg dry weight of material in each square meter and gross primary productivity may be approximately 1 kg of carbon per square meter per year. Of this, nearly one third is used in respiration, a similar amount used for production of leaves, with about 14% for the production of its subsurface root and rhizome system. The remaining quarter is divided between storage, production and development of reproductive structures, and excretion of dissolved organic matter. Even this latter, usually un noticed, component is one of the key inputs into the microbial food chain, which later becomes available to larger organisms.

The depth range of seagrasses is generally limited by illumination in the Gulf to fairly shallow depths. Light is probably the most important factor determining depth zonation and, in the Arabian Gulf where water is not especially transparent, a depth limitation of about 6-10 m is common, perhaps only half of this close to shore. Exceptionally, seagrasses have been found at 17 m depth far offshore (Basson, et al., 1977).



Quantitatively, the species Halodule uninervis is usually the dominant species in the Gulf, either forming large monospecific stands, or occurring in mixed stands with the other two species. Whatever their composition, the seagrasses form a very dynamic system, one which reflects the balance of new colonization, growth, trapping of sediments, and erosion or disappearance. Factors causing erosion and disappearance have, in recent times, become very severe and are caused to great extent by the increasing pace of industrialization along the seashore.

In sheltered locations, flat, homogeneous meadows are formed, but where topography or currents are more varied, sub tidal seagrass beds may have a greater mixture of species, and may occur with a mixture of a wide range of algae. In the Gulf, more than in many tropical locations, the development of seagrass beds is influenced strongly by seasonal weather and temperature. Some areas of sea bed which have a 90% cover of seagrass in summer, may see a drop to only one third of this density in winter (Vousden,1988).

Plate 5.10 Seagrass, Halophila stipulacea. Plate 5.9 Tube worm feeding by filtering water for zooplankton.

Plate 5.11 Seagrass, Halodule uninervis.



Seagrass blades generally have a coating of surface algae. Important among these are microalgae including nitrogen fixing cyanophytes. The fixed nitrogen can be transferred to the host seagrass, and so is an important factor contributing to the high productivity of seagrass ecosystems. One downside of the coating of microalgae might be that light penetrating to each seagrass blade is likely to be reduced, but here too, studies have shown that the biomass of such epiphytes is also seasonal, with more developing in the spring and summer when the sun strengthens, significantly minimizing the chances of light becoming limiting. Encrustations on seagrass blades also include attached forms of animal life such as hydroides, sponges, bryozoans and tunicates. These, in turn, attract other fauna notably molluscs, polychaetes, nematodes and very small crustaceans. Altogether in the Saudi Arabian Gulf a total of 530 different species associated with seagrasses was recorded by Basson, et al., (1977) with nearly one third being molluscs. About 10% of the species found in Gulf seagrass beds are found only in seagrass and nowhere else.

Seagrass beds have an important nursery function for commercial shrimp species and for pearl oysters, as well as for many other species of biological importance. Unsurprisingly, most of the species which use seagrass meadows in these ways are very small, which means that average numbers of individuals in seagrass beds can be huge; numbers exceeding 30,000 per square meter have been recorded. Such organisms naturally have short lifespans, showing that the biological turnover in seagrass beds occurs at a very fast rate.

Local studies on seagrass nursery functions have shown significant differences occurring between locations that are related to different physical conditions in different parts of the Gulf. In almost all cases however, the importance and abundance of seagrass habitats for fisheries nurseries is clear.

Plate 5.12 Mouth brooding cardinalfish hiding in seagrass.

Plate 5.13 Starfish feeding in the sand.

Plate 5.14 Hermit crab.



AlgaeMany of the hardgrounds in the Gulf are not dominated by corals but by algae. On many of the reefs too, cover by macroalgae may also be dominant. Large brown algae extending to 1 m tall or more may be abundant in many areas of the Gulf, in areas especially of high salinity and temperature, where these may be joined by significant quantities of green algae also. The algae communities in most of these areas show a strong seasonality and many species appear to the annual at least in terms of the fronds, although they may have substantial basal parts which persist for several years. Their seasonality is correlated with water temperature.

Macroalgae compete with corals for space in illuminated areas to a great extent. In areas close inshore, and in particular where salinity may be elevated and temperature extremes are greater, the seaweeds may take over from corals so that there is a change from a coral dominated to an algal dominated condition as physical stresses increase. Macroalgae are particularly common on the raised limestone platforms or domes in the Gulf, which do not appear to be actively accreting reefs. Competition between coral and algae is likely to be important in some offshore areas but nearer the shore the physical conditions tend to favor algae. Whether competition between corals and algae is direct or whether seasonal nutrient enrichment and temperature changes simply favor algae and disfavor corals in conditions of increasing environmental severity, is not always clear, but what is clear is that areas of the Gulf which are marginal from a coral reef viewpoint are commonly fairly central from the point of view of algae.

Algae attach to rock, not usually to soft substrate, although in sheltered areas of the Gulf they grow very well on the banks of rubble. They can even be found on sand where wave or current disturbance is low enough, although generally the attachment points are perhaps dead shells or dead fragments of coral. The main three taxonomic groups, the reds, greens and species of small browns, may occur together in this respect. Brown algae are generally restricted to shallower water; they tend to have the highest proportion of non-photosynthesizing tissues so they need a greater intensity of illumination. The large browns especially, such as Sargassum and relatives, thrive only in very shallow water where dense mats of tangled fronds from such species can be seen floating on the surface at low tide.

Turf algae and algae lawns

Many rocky areas, particularly coral reefs, support assemblages of coralline algae and small brown and green algae which cover extensive areas in the shallows. These assemblages are composed of a diverse group of leafy or filamentous species usually 2 cm tall or less. These are significant sources of food for grazing herbivores and, while these algae grow very rapidly, they are equally rapidly cropped so that their standing biomass is never very large. This, however, conceals their fast productivity; they form the basis of a substantial part of the Gulf marine food chain. Several species of reef fish “farm” such areas, aggressively keeping other grazers at bay. The algal rate of production may be 1 to 3 g dry weight per square meter per day. Where patches are guarded by territorial fish, there may be about 1 to 2 weeks growth visible on the rock, while in areas which are not guarded by territorial fish the algae are more heavily grazed and the algal standing stock may only be about 3 to 4 days growth.

The characteristic of the Gulf seaweed community is the dominance of large brown algae, especially of the genera Sargassum, Cystoseira and Hormophysa. These may grow in dense stands or in more sparse and open manner, and either way they take the place of coral communities in many shallow areas. While they are characteristic of the Gulf, these macroalgal communities are not confined to the Gulf but are seen in many so-called marginal reef areas elsewhere, particularly those of higher latitudes where they gradually outcompete corals as conditions for corals become less favourable, such as in areas with increased nutrients. Around Saudi Arabia they are strikingly abundant in the southern Red Sea, for example, and in areas of Oman they are common where upwelling seawater is the driving force. In the Gulf, marginal conditions are generated more by extremes of temperature and salinity, as well as by rising nutrients. In all such areas there is a dramatic increase in the Fucales, the family which contains most of the above mentioned large brown algae.

It appears that little work has been done on the undoubtedly high productivity of these algal stands, nor on their associated fauna. Coles (1988) examined the question of temperature on the Gulf Coast of Saudi Arabia, where seasonal blooms of algae occur, which become dense enough to provide heavy shading of the corals growing on the hard substrate beneath. Sargassum can cover up to 85% of shallow hardgrounds in some areas where water temperatures and salinity are high. In the Gulf though, elevated nutrients do not seem to be necessary for such high densities of brown algae, unlike most examples seen in high latitude reefs. The controls of high cover macroalgae are therefore complex and still unclear, and certainly different algal species respond in different ways.

Plate 5.17 Algae, Sargassum heteromorphum. Plate 5.19 Axinellid sponge.

Plate 5.16 Algae, Sargassum sp. Plate 5.18 Damsel fish (Pomacentrus sp.).

Plate 5.15 Sea jelly in algae bed.


Overall, areas dominated by macroalgae are extensive in the Gulf, where, in most cases, the algae are fairly small species. However, striking areas of very large brown algae are highly conspicuous and characteristic of this region. Where the cover of algae exceeds a certain point at the expense of corals, the substrate will cease to be an accreting coral reef and becomes instead an algal dominated platform.

Throughout the shallow, hard substrate areas, there exist a particular functional group of algae worthy of separate mention. These are the calcareous algae, and they are a particularly important group whose characteristic is that they, like corals, deposit limestone. There are two functional kinds in this respect. Some, belonging to the red algal taxonomic group, deposit solid, durable accretions of limestone in a way similar to corals, and indeed they look rather like pink stone. These commonly occur on reefs where they are an important component of the accreting biota. Other calcareous algae remain leafy, forming discs and spindles, whose limestone material eventually becomes part of the sand when the fronds die. Their importance comes partly from the rapid rate at which they can generate limestone, sand and sediment.

Plate 5.20 Goby fish (Microgobius gulosus) in oyster shell. Plate 5.21 Sponge in algae lawn (Phylum Porifera).

Plate 5.22 Flat toadfish hiding in algae lawn (Austrobatrachus dussumieri).

Plate 5.24 Brown algae, Dictyota sp. Plate 5.23 Oyster in algae lawn.



Plate 5.25 Jellyfish, Crambionella orsini.

Plate 5.27 Nudibranch (Phylum Mollusca).

Plate 5.28 Glowing jellyfish (Phylum Cnidaria) near Jana Island.

Plate 5.26 Sea nettle jellyfish (Chrysaora sp.).



{Avrainvillea riukiuensis Yamada}

Cladophorales Cladophoraceae Chaetomorpha aerea (Dillwyn) Kützing Chaetomorpha gracilis Kützing Chaetomorpha ligustica (Kützing) Kützing Synonym: Rhizoclonium tortuosum (Dillwyn) Kützing Chaetomorpha linum (O.F. Müller) Kützing Chaetomorpha linum f. brachyarthra (Kützing) Børgesen Chaetomorpha mediterraea (Kützing) Kützing Cladophora cf coelothrix Kützing {Cladophora dalmatica Kützing} {Cladophora echinus (Biasoletto) Kützing} {Cladophora herpestica (Montagne) Kützing} Cladophora koeiei Børgesen Cladophora nitellopsis Børgesen Cladophora sericoides Børgesen {Rhizoclonium implexum (Dillwyn) Kützing}

Dasycladales Polyphysaceae Acetabularia calyculus Lamouroux in Quoy and Gaimard Siphonocladales Boodleaceae Cladophoropsis herpestica (Montagne) Kützing Cladophoropsis sundanensis Reinbold Siphonocladaceae Dictyosphaeria cavernosa (Forsskål) Børgesen {Valonia utricularis (Roth) C. Agardh} Ulotrichales Gomontiaceae Gomontia polyrhiza (Langerheim) Bornet and Flahault Ulvales Phaeophilaceae Phaeophila dendroides (Cruan and Cruan) Batters Ulvellaceae Entocladia viridis Reinke Ulvaceae Enteromorpha clathrata (Roth) Greville Ulva flexuosa Wolfen Ulva intestinalis L. Synonym: Enteromorpha intestinalis (L.) Nees Ulca lactuca L. Ulva reticulata Forrskål

Heterokontophyta (Phaeophyta) Dictyotales Dictyotaceae

Dictyopteris polypodioides (De Candolle) Lamouroux Synonym: Dictyopteris membanacea (Stackhouse) Batters Dictyota cervicornis Kützing Synonym: Dictyota indica Sonder {Dictyota dichotoma var. intricata (C. Agardh) Greville} Dictyota friabilis Setchell Lobophora variegata (Lamoroux) Womersley ex Oliveira Padina boergesenii Allender and Kraft Padina gymnospora (Kützing) Vickers Padina minor Yamada Ectocarpales Acinetosporaceae Feldmannia indica (Sonder) Womersley and Bailey

Chlorophyta Bryopsidales Bryopsidaceae Bryopsis hypnoides Lamoroux Trichosolen maritianus (Børgesen) Taylor Caulerpaceae Caulerpa sertularioides (S.G. Gmelin) Howe {Caulerpa sertularioides var. farlowii (Weber van Bosse) Børgesen}

Codiaceae Codium papillatum Tseng and Gilbert Udoteaceae Avrainvillea amadelpha (Montagne) Gepp and Gepp

Algae Species recorded for the Saudi Arabian CoastSince the first description of marine algae (seaweeds) from the Arabian Gulf by Endlicher and Diesing (1845) there have been several studies which have included species recorded from the Arabian Coast and adjacent regions (Al Hasan and Jones, 1989; Basson, et al., 1989; Basson, 1992; Børgesen, 1939; Newton 1955a, 1955b; Nizamuddin and Gessner, 1970) and a few of the algal flora of the Saudi Arabian Coast of the Arabian Gulf in particular (Basson 1979a, 1979b; De Clerck and Coppejans, 1996; De Clerck and Coppejans, 1994; Khoja 1998, 2000). However, the flora of the Saudi Arabian Coast of the Gulf is still little studied in detail other than a few localized areas such as the Jubail Marine Wildlife Sanctuary, and further collection is certain to result in an increase in the algal flora.

The seaweed species recorded for the Gulf Coast of Saudi Arabia are listed. This list has been compiled from published records and the taxonomy has been updated to the currently accepted names. Species recorded from Bahrain (Basson, et al., 1989; Basson, 1992; Newton, 1955a; Silva, et al., 1996) are also included (indicated by {} in the text), as it is very likely that they also occur on the adjacent Saudi Arabian Coast.

Plate 5.29 Brown algae, Sargassum decurrens.



Feldmannia irregularis (Kützing) Hamel Hincksia mitchelliae (Harvey) Silva Chordariaceae {Myriactula arabica (Kützing) Feldmann} Nemacystus decipiens (Suringar) Kuckuk Nemacystus erythraeus (J. Agardh) Sauvageau Fucales Cystoseiraceae Cystoseira myrica (S.G. Gmelin) J. Agardh Cystoseiria trinodis (Forsskål) C. Agardh Hormophysa cuneiformis (J.F. Gmelin) Silva Sargassaceae Sargassum angustifolium (Turner) J. Agardh Sargassum asperifolium Hering and Martens ex J. Agardh Sargassum boveanum J. Agardh Sargassum boveanum var aterrimum Grunow {Sargassum cervicorne Greville} {Sargassum crassifolium J. Agardh} Sargassum decurrens (Brown ex Turner) C. Agardh Sarhassum heteromorphum J. Agardh Sargassum latifolium (Turner) C. Agardh Sargassum oligocystum Montagne Sargassum binderi Sonder {Sargassum swartzii C. Agardh} Turbinaria conoides (J. Agardh) Kützing Turbinaria ornata (Turner) J. Agardh

Scytosiphonales Scytosiphonaceae Colpomenia sinuosa (Mertens ex Roth) Derbès and Solier Hydroclathrus clathratus (C. Agardh) Howe Sphacelariales Sphacelariaceae Spacelaria rigidula Kützing Sphacelaria tribuloides Meneghini

Rhodophyta Bangiophyceae

Erythropeltidales Erythrotrichaceae Erythrocladia irregularis Rosenvinge Erythrotrichia carnea (Dillwyn) J. Agardh

Stylonematales Stylonemataceae Chroodactylon ornatum (C. Agardh) Bassoon

Florideophyceae Acrochaetiales Acrochaetiaceae Acrochaetium bahreinii Børgesen Acrochaetium robustum Børgesen Acrochaetium savianum (Meneghini) Nägeli Bonnemaisoniales Bonnemaisoniaceae Asparagopsis taxiformis (Delile) Trevisan

Ceramiales Ceramiaceae Antithamion cruciatum Nägeli Centroceras clavulatum (C. Agardh) Montagne Ceramium cimbrium f. flaccidum (Petersen) Furnari and Serio Synonym: Ceramium fastiguatim f. flaccidum Petersen

Ceramium codii (Richards) Feldmann-Mazoyer Ceramium cruciatum Collins and Hervey Ceramium deslongchampsii Chauvin ex Duby Ceramium luetzelbergii Schmidt Ceramium maryae Weber van Bosse Ceramium subverticillatum (Grunow) Weber van Bosse {Gayella flaccida (Harvey ex Kützing) Cho and McIvor Synonym: Ceramium flaccidum (Harvey ex Kützing) Ardissone} Gayliella transversalis (Collins & Hervey) Cho and Frederiq Callithaniaceae Crouania attenuata (C. Agardh) J. Agardh Spyridiaceae Spyridia filamentosa (Wulfen) Harvey Dasyaceae Dasya anastomosans (Weber van Bosse) Wynne Synonym: Dasyopsis pilosa (Weber van Bosse) Millar Dasya baillouviana (S.G. Gmelin) Montagne Dasya ocellata (Grateloup) Harvey Dasya pedicellata C. Agardh Heterosiphonia crispella (C. Agardh) Wynne Delesseriaceae Hypoglossum sp. Rhodomelaceae Acanthophora spicifera (Vahl) Børgesen Chondria collinsiana Howe Chondria dasyphylla (Woodward) C. Agardh {Chondria cornuta Børgesen} Chondrophycus papillosus (C. Agardh) Garbary and Harper Synonym: Laurencia papillosa (C. Agardh) Greville Chondrophycus patentirameus (Montagne) Nam Synonym: Laurencia patentiramea (Montagne) Kützing Digenea simplex (Wulfen) C. Agardh Herposiphonia dendroidea Nägeli Herposiphonia secunda f. tenella (C. Agardh) Wynne {Laurencia glandulifera (Kützing) Kützing} Laurencia obtusa (Hudson) Lamouroux Laurencia paniculata (C. Agardh) J. Agardh Leveillea jungermannoides (Hering and Martens) Harvey Polysiphionia crassicolis Børgesen Polysiphonia denudata (C. Agardh) Zanardini Polysiphonia kampsaxii Børgesen Polysiphionia opaca (C. Agardh) Moris and De Nortaris Polysiphonia scopulorum var villum (J. Agardh) Hollenberg Polysiphonia tuticorinensis Børgesen Wrangeliaceae Anotrichium tenue (C. Agardh) Nägeli Corallinales Corallinaceae Amphiroa fragilissima (L.) Lamouroux Fosliella farinose (L.) Howe Hydrolithon farinosum (Lamouroux) Penrose and Chamberlain {Jania pumila Lamouroux} Jania rubens (L.) Lamouroux Lithophyllum kotchyanum Unger Sporolithaceae Sporolithon molle (Heydrich) Heydrich Ceramiales Ceramiaceae Antithamion cruciatum Nägeli Centroceras clavulatum (C. Agardh) Montagne Ceramium cimbrium f. flaccidum (Petersen) Furnari and Serio Synonym: Ceramium fastiguatim f. flaccidum Petersen



{Mastigocoleus testareum Langerheim ex Bornet and Flahault} Microchaetaceae {Microchaete grisea Thuret} Microcystaceae {Microcystis zanardinii (Hauck) Silva} Nostocaceae {Anabaena pseudooscillatoria Bory de saint-Vincent Nodularia spumigena var. major (Kützing) Bornet and Flahault Nostoc punctiforme (Kützing) Hariot Rivulariaceae {Calothtix confevicola (Roth) C. Agardh ex Bornet and Flahault} {Calothrix crustacea Schousboe ex Thuret} Oscillatoriales Amatoideaceae Homeothrix varians Geitler Borziaceae Borzia trilocularis Cohn ex Gomont Oscillatoriaceae Blennothrix cantharidosma (Gomont ex Gomont) Anagnostidis and Komarek Synonym: Hydrocoleum cantharidosmum Gomont ex Gomont {Leibleinia epiphytica (Hieronymus) Compère} Lyngbya aestuarii (Mertens) Liebman ex Gomont Lyngbya ceylanica var. constricta Frémy Lyngbya confervoides C. Agardh ex Gomont Lyngbya majuscula (Dillwyn) Harvey ex Gomont Phormidiaceae Coleofasciculus chthonoplastes (Thuret ex Gomont) Siegesmund, Hohans and Friedl Synonym: Microcoleus chthonoplastes Thuret ex Gomont {Microcoleus vaginatus (Voucher) Gomont ex Gomont} {Phormidium corallinae (Gomont ex Gmont) Anagnostidis and Komarek} {Pophyrosiphon notarisii (meneghini) Kützing ex Gomont} Schizotrichaceae {Schizothrix calcicola (C. Agardh) Gomont ex Gomont} {Schizothrix mexicana Gomont} {Schizothrix tenerrima Kützing} Pseudoanabaenales Pseudoanabaenaceae {Heteroleibleinia inflexa (Frémy) Anagnostidis and Komarek} {Spirulina subsalsa Örsted} Spirulina subtillisima Kützing {Spirulina tenerrima Kützing

Ceramium codii (Richards) Feldmann-Mazoyer Ceramium cruciatum Collins and Hervey Ceramium deslongchampsii Chauvin ex Duby Gelidiales Gelidiellaceae {Gelidiella acerosa (Forsskål) Feldmann and Hamel} Gelidiella myriocladia (Børgesen) Feldman and Hamel Gelidiaceae Gelidium pusillum (Stackhouse) Le Jolis Gigartinales Areschougiaceae {Sarconema filiforme (Sonder) Kylin} Dumontiaceae Dudresnaya sp. Cystocloniaceae

Hypnea cornuta (Kützing) J. Agardh Hypnea musciformis (Wulfen) Lamouroux Hypnea spinella (C. Agardh) Kützing Synonym: Hypnea cervicornis J. Agardh {Hypnea valentiae (Turner) Montagne} Peysonneliaceae Perssonelia simulans Decaisne Solieriaceae Wurdemannia miniata (Sprengel) Feldmann & Hamel Nemaliales Liagoraceae Liagora distenta (Mertens ex Roth) Lamouroux Rhodymeniales Champiaceae {Champia globulifera Børgesen} Champia parvula (C. Agardh) Harvey

Cyanobacteria Chroococcales Chroococcaceae Chroococcus membranius (Meneghini) Nägeli {Chroococcus minutus (Kützing) Nägeli} Chroococcus turgidus var, maximus Nygaard Chroococcus varius A. Brown Cyanobacteriaceae {Aphanothece stagnina (Sprengel) A. Braun} Dermocarpellaceae Cyanocystis hemisphaerica (Setchell & gardner) Kaas Synonym: Dermocarpa hemisphaerica Setchenn & Gardner {Dermocarpa acervata (Setchell & gardiner) Pham-Hoàng Hô} Entophysalidaceae {Entophysalis conferta (Kützing) Drouet & Daily} {Entophysalis deusta (Meneghini) Druet & Daily} {Johannesbaptistia pellucida (Dickie) Taylor & Druet} Gomphosphaeriaceae Gomphosphaeria aponina Kützing Hydrococcaceae {Hyella caespitosa Bornet & Flahault} vPleurocapsa fuliginosa Hauck

Synechococcales Merismopediaceae Merismopedia glauca (Ehrenberg) Kützing Nostocales Hapalosiphonaceae

At present a total of 110 species of seaweeds have been recorded from the Saudi Arabian Coast of the Arabian Gulf; 27 species of Chlorophyta, 29 species of Heterokontophyta (Phaeophyta), 59 species of Rhodophyta and 18 species of Cyanobacteria. More species are likely to be described in future studies. The diversity of macroalgae on the Coast of Saudi Arabia in the Arabian Gulf is reasonably diverse when compared to other regions of the Gulf (Price, et al., 2006; Schils and Wilson, 2006), but the limited number of studies means that the diversity is probably underestimated and further collections are likely to result in an increase in the number of species recorded.



Plate 5.31 Tube worm in algae bed.

Plate 5.33 Hermit crab with anemone.

Plate 5.30 Barred arab blenny (Omobranchus fasciolatus). Plate 5.34 White hydroid, Macrorhynchia sp.

Plate 5.35 White tentacles of a tube worm.

Plate 5.36 The tentacle tips of a sea anemone.

Plate 5.37 Starfish, Astropecten sp.

Plate 5.32 Sea cucumber, Holothuria atra.



Coral Reefs

A map showing the distribution of major coral reefs along the coast (Figure 5.1) shows that they are scattered and not especially abundant. Nevertheless, their diversity and productivity is extremely high and is disproportionate to their comparatively small area.

Some of the earliest studied coral reefs in the Gulf were those of the islands off the Coast of Saudi Arabia (Basson, et al., 1977). Between these, and between the islands and the mainland, the water is very shallow and, while the sea bed is generally a habitat of soft substrate and unsuitable for most corals, there are in addition numerous patch reefs populated to some extent by a scattering of corals which in some places are fairly abundant.

Reef distributionsBecause salinity increases southward along the coast with the highest concentrations occurring in the Gulf of Salwah (Basson, et al., 1977; KFUPM/RI 1988, 1990), the number of coral reefs decreases gradually from Abu Ali south to Ras Tanura and declines dramatically from Ras Tanura southeast towards, and reaching the West Coast of Bahrain, and down to Qatar (Basson, et al., 1977; IUCN, 1988). Coastal reefs are located at Abu Ali, Umm al Jamal (south of Jurayd Island), Abu Safah, Fasht Al Eling and Fasht An Najwah (northeast of Dammam, Basson, et al., 1977; SATTL, 1984; IUCN, 1988), Fasht Al Jarim (north of Bahrain) and Tarut Bay (KFUPM, 1988). Coral colonies surviving in the intertidal and shallow coastal waters were also observed from places such as Safaniya and Ras Tanura. In the Gulf there is no clear-cut distinction between platform and fringing reefs (Basson, et al., 1977). Some of the larger platform reefs have created unstable sand banks around their tops which are exposed during low tide periods. The best known examples of Saudi Gulf reefs are the much smaller number of reefs which have formed more permanent sand islands some of which have formed beach rock by cementation of the more stable sand.

The present day reefs and coralsAny account of the reefs of the Gulf is greatly complicated by the fact that the past 15 years or so has seen huge changes in their component corals. Substantial peaks in seawater temperature in 1996, 1998 and on two more occasions in the 2000s killed enormous numbers, especially of the shallow-living Acropora species. Until these warming events, the shallow and mid-depth parts of reefs were dominated by species of this fast-growing branching coral genus but, following the massive warming events, these died in huge numbers. For a while, usually for two to three years, the skeletons of these corals remained in place, increasingly covered with films of filamentous algae and gradually disintegrating. Then, the increasingly eroding dead branches started to crumble, turning shallow areas of reef into areas of mobile coral rubble, especially nearer the shore. In several cases in the Gulf, these have not recovered, while some have recovered very little. However, reefs further offshore show signs of greater recovery of these susceptible, framework forming species. Today, the dominant corals therefore have tended to be of different, more thermally tolerant groups.

Plate 5.38 Diver filming richness of life on the Jana Island coral reef.


Most reefs, especially those well removed from land, show the typical reef profile consisting of reef flats at or near low water level, and reef slopes which descend relatively steeply to meet the soft substrate beneath it. At the junction with the soft substrates is a third zone, the reef base, where corals and coral rock become increasingly sparse, and containing several more sediment resistant species. Basson, et al., (1977) sub divide these three basic zones, on the offshore islands at least, into as many as 12 different categories. On reefs nearer shore, the reef slopes usually have a more gentle slope, one which is much shorter overall than is typical of, for example, the Red Sea or Indian Ocean generally. Indeed some coral reefs near land are often no more than a gentle, elevated slope which gradually shallow to the low water level, although many, perhaps most, do not reach to the surface of the sea. Many of these may more accurately be termed hardgrounds which support coral communities, rather than being true, actively accreting reefs.

Following the severe warming events, zones which previously were occupied by branching Acropora corals have, in large part, become denuded of these species. Today, the most vigorous new colonizers are usually Faviid genera, smaller mounds of the brain coral Platygyra and the star coral Favia. While they have always been present, these may now be benefiting from the newly released space, and although they cannot replicate the substantially three-dimensional structure previously provided by the branching Acropora, they are providing substantial coral cover once again.

Another major genus is Porites. These always formed the largest colonies and still do in possibly most places. They were remarkably resistant to warm water, as was also the case in much of the Indopacific ocean. They remain one of the major reef builders of the Gulf. Today, because of the recent mass mortalities of coral, the zonations on these reefs are in a state of relatively rapid flux.

Plate 5.39 Undulated moray, Gymnothorax undulates.

Plate 5.40 Diversity of the reef corals.



The coral speciesThere is a clearly distinct Arabian subset of corals, composed partly of those which are highly tolerant to harsh environmental conditions, joined (in the Red Sea more than in the Gulf) by several endemic species. Within the Arabian region itself, six groupings can be seen, one of which is the Gulf with about 60 species. Only a very few soft coral species join them, though these are limited to the east of the Gulf. The true number of coral species is probably greater than 60, though the taxonomy of some is still a little unsure. Probably almost all of these will be seen around the offshore islands, with fewer surviving as conditions towards shore experience greater salinity and greater fluctuations in temperature between summer and winter.

Many older accounts of the corals in the Gulf, with their descriptions of the main reef building species, are now obsolete for the reasons noted above. No longer is there a clearly defined, shallow zone of Acropora. Although this group of corals is showing some recovery, with many large and spectacular colonies on reefs furthest from shore, their recovery in most areas inshore is extremely limited and this group is being replaced by others of more massive form. Today, probably the main reef building group are Porites which survived well and which form large solid expenses of living coral. Porites cf. compressa is the primary reef builder and most common coral in the northern nearshore reefs from Safaniya south to Abu Ali though it is nearly absent or rarely found from the eastern tip of Abu Ali to Tarut Bay in the southern area. In future, increasingly large colonies of Favia and Platygyra may become increasingly dominant. While in the past, Acropora clathrata was quite commonly observed on reef tops in the nearshore platform reefs in the northern area, these table shaped corals have largely disappeared from these reefs since the late 1980s (KFUPM/RI, 1988; Coles and Fadlallah, 1991).

Plate 5.41 Platygyra Corals with Table Coral Acropora.

Plate 5.42 Platygyra sp.

Plate 5.44 Coral Porites sp.

Plate 5.43 Coral Acanthastrea sp.


marine atlas of the western arabian gulf - saudi … · 116 marine atlas of the western arabian...

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