Brownlie, G

Hall-Spencer, JM

Hamid, A

Henderson, C

Kinchington, A

Linklater-McLennan, R

Mokhtar, H

Hall-Spencer, Jason

Plymouth Electronic Archive and Research Library

The first ecological study of aRed Sea maerl bedCORE SAMPLINGFauna and flora were collected in 15 cm long x 10 cmcircumference cores on four biotopes; sand 6 cores, seagrass6 cores, centre of maerl area 12 cores, edge of maerl 6 cores.Samples were sieved (1 mm mesh) and placed in plastic bagswith 8% formalin (Fig. 3) then labelled and transported toGlasgow University for counts and identification. Thesamples have been sorted into major Phyla and are now beingidentified to Family, counted and weighed.INTRODUCTIONMaerl (Corallinaceae, Rhodophyta) forms a living graveldeposited by unattached calcified red algae - its highly branchedform provides protection for many invertebrate species.Scotland is home to some of the most extensive maerl beds inEurope but in 2001 Glasgow University students found a maerlbed within Nabq Managed Resource Protected Area, South Sinai,Egypt.  Maerl has not previously been described in the Red Sea,so in 2002 a return trip was made to study the site in detail. Thisposter summarises the findings.          The maerl occurred in a lagoon sheltered by an outerfringing reef with an inner fossil patch-reef that was covered inbranched coralline algae.  We observed that chunks of this algaewere undermined by burrowing sponges and polycheates andcould break off and form rhodoliths.  Wave action had causedrhodoliths to accumulate in the lee of the reef flat.  Inshore of thereef, calm lagoonal conditions allowed the rhodoliths (Fig. 1) togrow into delicately branching maerl beds (Fig. 2).METHODSThe lagoon biotopes were mapped using three parallel transectsmarked from the beach to the fringing reef.  Depth, time andsubstratum type were recorded at 10 m intervals along thetransects.  Depths were later related to Chart Datum.  At high andlow tide, physical factors were measured at 60 m, 150 m and 220m along the mid-transect line covering sand, maerl and sea grassbiotopes respectively.  Water/air temperatures were noted andcurrents were measured by timing a neutrally buoyant object over5 m.  Horizontal underwater visibility (to measure turbidity) andnear-bottom salinities were measured.  Prevailing winds wereestimated using the Beaufort scale..References:Foster, M.S,  (2001) Rhodoliths:between rocks and hard places. J.Phycol.37,659-667Hall-Spencer, J.M, (1998) Conservation issues relating to maerl beds as habitatsfor molluscs.  J. Conch. Spec. Publ. 2, 271 - 286AcknowledgementsThanks to South Sinai Protectorates Division (Egyptian EnvironmentalAffairs Agency) for their help and support and to the British Council for part-funding the expedition.PRELIMINARY FINDINGSThe maerl has been identified as Neogoniolithion sp. and isproduced by a ‘rhodolith factory’ on the leeward fossil reefplatform. Calm conditions within the lagoon allow finelybranched thalli to develop - live maerl was only found >30cm water depth but it could withstand a wider range oftemperature and salinity than that found on the outer reef.The maerl requires light, for photosynthesis, coupled withcurrents to prevent smothering by silt.       Preliminary results show that the maerl harbours anoutstanding diversity of associated fauna, particularlyPolychaeta, Crustacea and Mollusca. Grazers are verycommon which may explain why the calcified algae are ableto compete with the seagrasses and algae within the lagoon.Once core analyses are complete we hope to provide the firstecological description of this rich Red Sea habitat.Table 1. Physical environmental conditionsPosition on reef Temperature (ºC) Current (m s-1)  Turbidity (m) Salinity(º/oo) Inner (60 m, sand) 28.5 - 34.0 1.7 –7.0 0.6 – 9.0 45 - 48Mid (150 m, maerl) 29.0 - 31.0 4.2 – 6.0 8.0 – 16.0 43 Outer (220 m, seagrass) 28.5 - 30.0 3.6 – 6.0 12.0 – 23.0 42 - 43  2. Maerl1. Rhodoliths3. Core sample sieving,preservation and sortingGreig Brownlie1, Jason Hall-Spencer2, Abdel Hamid3, Clare Henderson1, AmandaKinchington1, Roxana Linklater-McLennan1, Hamdy Mokhtar31Division of Environmental and Evolutionary Biology, University of Glasgow, GlasgowG12 8QQ, Scotland. 2University Marine Biological Station, Millport, Isle of Cumbrae,KA28 0EG, Scotland. 3Dept. Marine Sciences, Suez Canal University, Ismailia, Egypt.

The first ecological study of a Red Sea maerl bed.

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The first ecological study of a Red Sea maerl bed.

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