N. Jb. Geol. Palaont. Abh. 297/2, 155-170Stuttgart, February 2013
Article
The foraminifera from the Bazaruto Archipelago (Mozambique)
Martin R. Langer, Jens M. Thissen, Walid A. Makled, and Anna E. WeinmannWith 8 figures and 1 table
LANGER,M.R., THISSEN,J.M., MAKLED,W.A. & WEINMANN,A.E. (2013): The foraminifera from theBazaruto Archipelago (Mozambique). - N. lb. Geol. Paliiont. Abh., 267: 155-170; Stuttgart.
Abstract: The Bazaruto Archipelago in the western Indian Ocean is home to a diverse reef biotaand a notable tourist attraction along the coast of Mozambique. Analyses of shallow-water reefal andlagoonal sediments from Bazaruto Island reveal two diverse assemblages of benthic foraminifera.The assemblages occupy three major environments and sedimentary regimes and are indicative ofreef, channel and lagoon facies. Species richness, Fisher a analyses, assemblage composition, andpercentage abundances of larger-symbiont-bearing foraminifera are mirrored in the cluster analy-ses. In general, the reef environments on the eastern side of Bazaruto Island harbor more species,higher percentages of larger symbiont-bearing, agglutinated, and hyaline-perforate foraminifera. Incontrast, the lagoon facies is characterized by high numbers of smaller miliolid foraminifera. Thecurrent-dominated open ocean channel environments south of Bazaruto Island are subject to extremewinnowing and house low-diverse assemblages, reflecting areas of wave-transport accumulation andredistribution. Among the larger benthic foraminifera from Bazaruto, species of the genus Amphiste-gina are prominent producers of calcium carbonate. They contribute substantially to the carbonatebudget and provide support to the framework and stability of reefal structures. Because of theirabundance and role as prominent carbonate producers, amphisteginid foraminifera can be consideredecosystem engineers. The distinct differences between reef and lagoon faunal assemblages imply lowhorizontal transport rates. Thus, the autochthonous benthic assemblages may preserve the originalcommunity structure and sufficient environmental information to be useful indicators for paleoeco-logical studies.
The National Park of the Bazaruto Archipelago (Mo-zambique) is known for its diverse marine habitats in-cluding mangrove forests, coastal sand dunes, rockyshores, seagrass meadows and coral reefs. The parkcovers a total marine area of 1430 km2 in which a richbiodiversity includes 2000 species of fish, 100 speciesof scleractinian corals, abundant invertebrates, andmore than 40 reptile taxa. The north-south oriented
archipelago is situated just ~20 km off the coast ofMozambique and consists of five islands: Bazaruto,Benguera, Magaruque, Santa Carolina (Paradise Is-land) and Bangue (Fig. 1). The Bazaruto Islands ex-tend between 21 °30' Sand 3S026' E and 21 °47' Sand37°27' E, and are located in the province of Inham-bane, between the Vilankulos and Inhassoro districts.The islands are composed of large sand bodies anddunes deposited during marine transgressions, possi-bly as early as Marine Oxygen Isotope Stage 5 (ARMIT-
Fig. 1. Location of the study area along the eastern coastline of Mozambique (inlet) and map of the Bazaruto IslandArchipelagowith samplingsites (stars)and samplenumbers.
AGEet al. 2006). These deposits are mostly erosionalproducts from the mainland that were transported bythe Limpopo and Save rivers.
Bazaruto is the largest of all the islands, approxi-mately 37 km long and up to 7 km wide, and hometo the largest dugong population between Somalia andthe Cape in South Africa (Dugong dugong, up to 250individuals). Despite its rich diversity of vertebratesand invertebrates, studies on the species richness ofprotists and other microbial primary producers areoverlooked. The present paper documents the speciesoccurrences, species richness, Fisher a diversity, anddistribution of benthic foraminifera from around Ba-zaruto Island to provide data for the interpretation ofregional species biogeography and habitat preferences.Detailed information on the species biogeographicdistribution and autecology will be presented later. Weintend the dataset to be useful in paleoecological stud-ies of raised reefs and lagoons along the coast of east-ern Africa (e.g., McMILLAN1986; DALE& McMILLAN1999; ARMITAGEet al. 2006).
The shallow water coastal areas of Mozambiquecontain highly diverse assemblages of foraminifera,but they are known only from a few geographicallydisparate places. One extensive area from which shal-low-water foraminifera are virtually unknown is theBazaruto Island Archipelago. Foraminifera from thecoast of Mozambique were previously studied by HER-ON-ALLEN& EARLAND(1915), BRAGA(1961), MOURA(1965), and MAKLED& LANGER(2010). HERON-ALLEN& EARLAND(1915) recognized 465 species of foramin-ifera at depths between 0 and 25 m from the KerimbaArchipelago, between Pemba Bay in the south (13°S)and Capo Delgado in the north (10°40 S). BRAGA(1961)identified 270 species at depths between 16 and 700meters from the area between Inhambane (23°5 S) andMaputo (26° S). MOURA(1965) studied the intertidalfauna from Inhaca Island and reported a total of 102species of foraminifera. MAKLED& LANGER(2010)provided the first report of benthic foraminifera fromBazaruto Island and documented the preferential se-lection of titanium minerals for test construction in
The foraminifera from the Bazaruto Archipelago (Mozambique) 157
Table 1. Sample site information (see also Fig. 1)with percentages oflarger symbiont-bearing (LBF) and smaller foraminifera(SF), number of species and Fisher a indices, and facies type of individual samples.
Sample Location Depth LBF SF Number of Fisher aNo. Longitude Latitude (m) (%) (%) species indices Facies type
Textularia hauerii D'ORBINGY.Related studies on fora-minifera from the southwestern Indian Ocean wereconducted as early as 1876 and include: WRIGHT(1876,1877), MOBIUS (1880), BRADY (1884), EGGER (1893),HERON-ALLEN& EARLAND(1915), BRAGA(1961), Mou-RA(1965), LECALVEZ(1965), MONIER(1973), BATTISTINIet al. (1976), PHLEGER(1976a, b), HOTTINGER(1977),PEREIRA(1979), CHASENS(1981), MONTAGGIONI(1981),BANNER& PEREIRA(1981), NEAGU(1982), LEVY(1982),McMILLAN (1986), COOPER & McMILLAN (1987),WRIGHTet al. (1990), DALE& McMILLAN (1998,1999),LANGER& HOTTINGER(2000), PERRY(2003), PERRY&BEAVINGTON-PENNY(2005), LANGER& SCHMIDT-SINNS(2006), and PIGNATTIet al. (2012). They cover the ad-joining countries of South Africa and Tanzania butalso Kenya and Somalia south of the equator.
2. Material and methods
The shallow reefal and lagoonal environments of theBazaruto Archipelago are characterized by warm wa-ters of the Indian Ocean with mean sea surface tem-peratures between 23° and 28°C, salinities of 35-35.4psu, and a maximum tidal flux of 3.8 meters (SCHLEYER& CELLIERS2005). Sediment samples containing fora-minifera were collected by M.L. while SCUBA divingand snorkeling in March 2003 by filling plastic bagswith substrata (algae, mud, sand, rubble, shells) fromthe top 2 em. The sample sites cover reefal, nearshore,
and island passage habitats and include: the inner andouter sides of the Two-mile Reef (sample 1811), thepassage between the Bazaruto and Benguera islands(sample 1762 and 1810), reefal sites north of WhaleRock Reef (samples 1770-1774), the Five-mile Reef(1781), and shallow lagoonal environments on theeastern side of Bazaruto at Indigo Bay (samples 1790,1800, 1820, for details see Table 1). These samplesvaried in the amount of material recovered. Becauseof the variability of substrates, the protocol was tomap and sample various habitats, and designed to bequantitative. All samples were washed over 63-}lmmesh sieves and dried, and the foraminifera were thenpicked from each. More than 5300 foraminifera wererecovered from the samples and identified to specieslevel, whenever possible; individuals in each specieswere counted.
Rarefraction was used in order to compare dis-parate samples (LUDWIG& REYNOLDS1988), whereforaminifera were picked from each sample until nonew species were discovered. This involved pickingand examining hundreds of specimens; only a fewsamples contained fewer than 100 specimens. Cumu-latively, 158 species of smaller and larger-symbiontbearing foraminifera (LBF) were identified and photo-graphed using Scanning Electron Microscopy (SEM).Our primary intention was to determine and illustratethe diversity of species and provide general environ-mental and biogeographic data useful in paleoecology
158 M.R. Langer et al.
3. Results
After the examination of 5352 foraminiferal specimensrecovered from sites around Bazaruto Island (Mozam-bique), a total of 158 species of benthic foraminiferawere identified (Figs. 4-8). The assemblage composi-tion comprises 97 porcelaneous, 44 hyaline-perforate,and 17 agglutinated species. They are assigned to 72genera. The ten most abundant taxa are: Amphisteginaspp., Elphidium d. E. limbatum, Heterostegina de-pressa, Peneroplis planatus, Planogypsina acervalis,Quinqueloculina bicarinata, Quinqueloculina d. Q.lamarckiana, Sorites orbiculus, Textularia hauerii,and Triloculina trigonula. In terms of absolute num-bers, species of the genus Amphistegina constitutealmost 40% of the total number of individuals count-ed. The ten most abundant genera include Amphiste-gina (39.67%), Quinqueloculina (11.41%), Triloculina(4.83%), Textularia (4.43%), Miliolinella (4.32%), El-phidium (4.17%), Peneroplis (3.03%), Pseudotriloculi-na (2.53%), Sorites (2.86%) and Spiroloculina (1.85%).
Foraminifera are among the most abundant testateprotists in the world's oceans and their shells representa major and globally significant sink for calcium car-bonate. Quantitative analysis of the sediment grainsrevealed that at some sites benthic foraminifera con-tribute up to 20% to the total number of carbonategrains. The numerical abundance data of foraminif-eral tests among all grains allows a first-order produc-tion estimate by using the equation of LANGER et al.(1997). Based on the abundance data the foraminiferalcontribution ranges between 0.1 and 0.8 kg CaC03 m2
yearl.
Fisher a
A
0,36
0,24
0,12
0,60
0,00
0,96
0,72
0,84
~ 0 ~ ;! r- ~ ~ ~ ~ 00 :5 ~ individuals and the total number of species (FISHER et~ 00 ro r- r- r- r- r- r- r- 00 00
al. 1943; Table 1).
Fig. 2. Q-mode cluster dendrogram from 12 samplesexhibitingtwo majorclustergroups.
1:;-.'".!!!"E 0,48Ui
and species distribution modeling (LANGER et al. andWEINMANN et al. submitted). Therefore, live foramin-ifera were grouped with dead tests because they con-stitute only a small percentage of the specimens in anysample. Thus, our samples are time-averaged and, assuch, provide an effective means of defining reefhabi-tats (GLENN-SULLIVAN & EVANS 2001).
To determine the structure in the foraminiferal dataset, a Q-mode cluster analysis using the Bray-Curtisdissimilarity and an R-mode cluster analysis usingthe Pearson's correlation coefficient was performed.These techniques grouped together samples with simi-lar faunal assemblages found in similar habitats (Figs.2-3). Foraminiferal assemblage diversity (Fisher a di-versity) was determined by using the total number of
3.1. Cluster analyses
Foraminifera III the Bazaruto Island reef systemcluster (Q-mode) into two groups (Clusters A and B,Fig. 2). They are associated with the major habitats andsedimentary regimes, and represent assemblages thatare typical for the eastern reefal or western shallow-water habitats. These are: 1.) reefal sites with livecoral coverage on the eastern site of Bazaruto Island(Cluster A), and 2.) shallow-water "lagoonal" siteson the western side off Indigo Bay (Cluster B). Twosamples collected in the channel separating Bazarutoand Benguera islands (sample No. 1762 and 1781) areassociated with the shallow-water Cluster B.
The foraminifera from the Bazaruto Archipelago (Mozambique) 159
Cluster A, from the wave-exposed side of Ba-zaruto, is associated with the prominent reefs and car-bonaceous sediments on the eastern side of the Island.These reefs playa vital role for the stability and growthof the island by providing protection and acting as cen-tres of carbonate production. The reefal structures arecovered by abundant scleractinian colonies. In pro-tected areas, where sand or algal biomass predomi-nates, patches of brownish detritus and undeterminedbacteria, diatoms, and algae occur on which abundantlive foraminifera accumulate. The sandy ocean flooris dominated by medium to fine-grained coral and al-gal sand. Robust and attached species dominate on thefore- and backreef sides ofthe reefs (e.g.Amphisteginaspp., Peneroplis planatus, Textularia hauerii, and So-rites orbiculus). Foraminifera are patchy in these areasbut, in some patches, they may be abundant and con-stitute 30% or more of the grains.
Cluster B from Indigo Bay aggregates the shallowlagoonal sites with those of the passage between Ba-zaruto and Benguera islands. It is associated with thefine- to medium-grained sand and algal environmentson the protected western side of the Island. The floorat Indigo Bay is fairly flat with a few small patch reefs,and is partly covered by seagrass and algae. The sedi-ment is rich in organic material as evidenced by thedark colour of the sediment below 2 cm. The IndigoBay environments contain a distinct, low-diversity andthin-shelled foraminiferal assemblage. It is dominatedby Peneroplis planatus, Amphistegina spp., Trilocu-lina trigonula and Pseudotriloculina d. P. oblonga.
3.2. Fisher a diversity
Species richness in the eastern reef Cluster A rangesbetween 1 and 141species. On the opposite site at In-digo Bay (sample #'s 1790, 1800 and 1820) taxonomicdiversity varies between 11 and 40. The sample siteswithin the island passage display a particularly lowspecies diversity, and ranges between 11 and 15. TheFisher a diversity indices calculated for all sedimentsamples show a wide range between 0.13 and 41.23(1-141 species). A high diversity group with 12 to 141species (Fisher a diversity indices between 2.34 and41.23) characterizes the exposed reefal sites on theeastern side of Bazaruto Island (samples 1770-1774).The highest Fisher a diversity value was recorded atsite 1771 (see Fig. 2), north of Whale Rock Reef. Thissample, alone, contained at least 141species of benthicforaminifera. Species richness in samples belongingto Cluster B ranges between 11 and 40, and Fisher a
0,96
0,88
0,80
0,721 2~
-'".!!!:~ 064U) ,
0,56
0,48
0,40
Fig. 3. R-modecluster dendrogramfor 21 genera from 12samplesexhibitingtwo majorclusterassemblages.
diversity values between 6.06 and 15.54. The lowestvalues were recorded at site 1810near the passage be-tween Bazaruto and Benguera Island (0.13). The shal-low-water samples collected from Indigo Bay result inFisher a diversity indices that range between 8.61 and13 (17-40 species).
The assemblage R-mode cluster analysis, basedon the most abundant genera, shows two major clus-ters (Fig. 3). Cluster 2 contains all larger foraminifera(except Peneroplis), some of the more prominent mi-liolid genera (Spiroloculina, Miliolinella, Quinquelo-culina, Pyrgo, and Triloculina), all agglutinated taxa(Gaudryina, Pseudoschlumbergerinia, Textularia),and elphidiid foraminifera. Cluster 1 is characterizedby smaller miliolids (Cycloforina, Pseudotriloculina),Peneroplis, and Planogypsina.
Among the species recovered, 4.71% (8 species) are
160 M.R. Langer et al.
larger symbiont-bearing foraminifera (LBF) harbor-ing endosymbionts. These taxa include: Amphisteginaspp., Amphisorus hemprichii, Borelis schlumbergeri,Coscinospira hemprichii, Heterostegina depressa,Peneroplis planatus, Sorites orbiculus, and S. vari-abilis. Larger symbiont-bearing foraminifera make up48.51% of the total number of individuals counted inall samples. Some of these taxa are prominent produc-ers of calcium carbonate and contribute substantiallyto the framework and stability of coral reefs (HALLOCK1981, 1999, 2002; LANGERet al. 1997; LANGER2008).The species most frequently encountered are membersof the genera Amphistegina and Heterostegina. Am-phisteginids are by far the most dominant taxon of allbenthics collected around Bazaruto. In terms of abso-lute numbers, amphisteginids contribute, on average,42.7% to the foraminiferal assemblages on the easternreef side of Bazaruto, and 10.51% to the protected In-digo Bay assemblages. At site 1810, near the passagebetween the islands, amphisteginids are present as aforaminiferal monoculture. Here, amphisteginids con-stitute 100% to the assemblage. In summary, the reefalsites generally contain higher numbers of larger fora-minifera than the western sites at Indigo Bay (Table 1).
Among the smaller, non-symbiont-bearing fora-minifera, the following species represent the 10 mostabundant taxa in all samples: Textularia hauerii(2.86%), Quinqueloculina d. Q. lamarckiana (1.46%),Elphidium d. E. limbatum (1.42%), Planogypsinaacervalis (1.29%), Q. bicarinata (1,29%), Triloculinatrigonula (1,18%), Q. sidebottomi (1,12%), Pseudotri-
loculina d. P. oblonga (1.07%), Q. poeyana (0.84%),and Pavon ina flabelliformis (0.82%). Prominent spe-cies of smaller, non-symbiont-bearing foraminifera onthe reefal sites are T. hauerii, Q. d. Q. lamarckiana,and E. d. E. limbatum. At the shallow lagoonal envi-ronments off Indigo Bay the following three speciesare particularly abundant: P. acervalis, T. trigonula,and Pseudotriloculina d. P. oblonga.
3.3. Reef and lagoon assemblages
The quantitative composition of foraminiferal assem-blages reveals distinct differences between the easternand the western sides of the island. Individuals of por-celaneous miliolid foraminifera are more abundant onthe western (61.06%) than on the eastern side of Baza-ruto Island (36.34%). The species richness of miliolidspecies, however, is significantly higher on the easternside (97 compared to 39 species on the western side).Hyaline-perforate foraminfera, in turn, are more abun-dant and more diverse on the eastern reef side thanon the western lagoonal side of Bazaruto (56.37%and 44 species vs 37.57% and 14 species). Among theforaminifera recovered from Bazaruto Island, 17 spe-cies have an agglutinated test. These taxa display anunequal distribution and are disproportionally moreabundant on the reefal eastern side of the Island. Whilethe shallow lagoonal environments house a total of 7species of agglutinated taxa, 17 species occur in thereef habitats. In terms of absolute numbers of individu-als, agglutinated taxa represent 7.29% of the total reefassemblages and only 1.37% at the lagoonal sites.
The foraminifera from the Bazaruto Archipelago (Mozambique) 161
Fig. 4.
162 M.R. Langer et al.
Fig. 5.
The foraminifera from the Bazaruto Archipelago (Mozambique) 163
4. Discussion
Foraminiferal species richness, cluster analyses re-sults, and Fisher a diversity patterns are distributedprimarily according to habitats (reef/lagoon) andsedimentary regime. Faunal clusters are character-ized by a number of dominant indicator taxa. Theseindicator taxa are numerically abundant but also mayoccur in low numbers in the other cluster (Fig. 2-3).On the eastern reef sites off Bazaruto Island, larger fo-raminifera are generally abundant on stable sedimentsubstrata of coral rubble covered by detrital or algalmats (Lipps & SEVERIN1986; HOHENGGERet al. 1999).Winnowing appears to take place in the ocean-currentdominated passage between Bazaruto and BengueraIsland. At some sites, amphisteginids are particularlyabundant (between 80 and 100%) indicating currentdominated assemblages sorted by size and shape ofindividual species of foraminifera. At all other sitesthe assemblages appear to be mostly autochthonous,indicating that dead individuals are not transportedfar, other than by gravity on steeper fore-reef slopes.The dominant species and the assemblages, in whichthey are found, preserve environmental informationthat can be applied to paleoecological interpretationsat other tropical reef and lagoonal sites.
Examination of species richness and Fisher a di-versity indices shows that the reefs and lagoons aroundBazaruto Island house diverse assemblages of benthicforaminifera (Fig. 2). A total of 158 species of fo-raminifera were recovered from a depth range between2 and 25 meters from around the islands (Figs. 4-8).This appears to be somewhat low compared to thestudies of 1.) HERON-ALLEN& EARLAND(1915) fromthe Kerimba Archipelago (465 species), 2.) BRAGA(1961) from the area between Inhambane and Maputo
(260 S; 270 species), 3.) BANNER& PEREIRA(1981) fromKenya (206 species), and 4.) PIGNATTIet al. (2012) fromSomalia (256 species). It needs to be noted, however,that the sampling size, the depth range analyzed, andthe types of environments sampled were significantlylarger in the latter studies. These factors may accountfor the larger species diversity recorded previously. Inaddition, BANNER& PEREIRA(1981) noted that HERON-ALLEN& EARLAND'S(1915) taxonomy requires revisionto update the systematics with modern species con-cepts. This exercise would probably reduce their totalnumber to approximately 350 taxa. The low number offoraminiferal taxa (102 species) identified by MOURA(1965) from Inhaca Island show that sampling size anddepth gradient have strong impacts on species counts.MOURA (1965) focused on intertidal foraminiferalassemblages. A landward decreasing diversity trendtowards shore also has been noted by PIGNATTIet al.(2012). They relate this trend to limiting environmentalfactors in stressed environments (i.e., salinity) that exertcontrol over the total number of foraminiferal taxa.
The computed Fisher a values for the Bazaruto Ar-chipelago reach peak values of 42 and are indicative ofhighly diverse environments. Peak values were record-ed in the reefal sites on the eastern coast of Bazaru-to Island. In contrast, the foraminiferal assemblagesfrom the Lamu Archipelago and the Burgao Channelfrom Somalia and Kenya translate to Fisher a valuesthat range between 1.5 and 29.9 (PIGNATTIet al. 2012).These lower Fisher a values are somewhat surprising,as the study sites at Lamu and Somalia are environ-mentally more diverse than the reefal and lagoonalsites around Bazaruto Island. The high foraminiferalspecies richness, thus, signifies that the Bazaruto Ar-chipelago provides environmental settings that pro-mote a rich biodiversity.
The foraminifera from the Bazaruto Archipelago (Mozambique) 165
Fig. 7.
166 M.R. Langer et al.
Fig. 8.
The foraminifera from the Bazaruto Archipelago (Mozambique) 167
Q-mode hierarchical cluster analyses reveals thattwo distinct cluster assemblages can be distinguishedaround Bazaruto Island: reefal habitats from the east-ern side, and shallow lagoonal environments fromIndigo Bay on the western side. Each assemblage ischaracterized by a specific range of Fisher a diversityindices, a set of dominant taxa, and specific species as-semblages. While reefal sites generally house a higherpercentage of larger, symbiont-bearing foraminifera,the assemblages from Indigo Bay contain a higherpercentage of smaller miliolids. In addition, aggluti-nated foraminifera are more abundant and diverse onthe reefal side of Bazaruto Island. The Q-mode clusterof foraminifera contrast with the nine cluster assem-blages reported from southern Somalia and easternKenya (PIGNATTI et al. 2012). This can be accountedfor by the diversity of habitats sampled by PIGNATTIetal. (2012) and includes mangrove flats, tidal channels,
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restricted shelf and open shelf environments, back andfore-reef sites, and carbonate and siliciclastic sedi-ments. The greater range of habitats and the steeperdepth gradient studied by PIGNATTI et al. (2012) mayexplain the higher number of species recorded in theirstudy (256/168 this study).
The species richness oflarger and smaller foramin-ifera in reefal habitats is certainly at the high end ofreefal sites reported, to date, from this region. It is alsoreflected in the total number of agglutinated, miliolid,and hyaline-perforate species that have their maxi-mum values on the eastern side of Bazaruto Island.In terms of absolute individual abundances, however,miliolid foraminifera are more abundant in the west-ern lagoonal settings off Indigo Bay.
Distinct differences between the assemblages fromthe east and west imply low horizontal transport ratesfrom reef to lagoon settings, and suggest that benthic
faunal transport around the island is limited. The re-distribution of dead or unattached foraminifera, how-ever, is rather common in areas where reef and lagoonare closely spaced (BANNER& PEREIRA1981). Areas ofwave-transport accumulations are particularly promi-nent within the ocean-current dominated passagebetween Bazaruto and Benguera islands. At this site,extreme winnowing by currents leads to drastic reduc-tions in foraminiferal species richness. Fossil assem-blages recovered from ocean floor sediments that ac-cumulated under strong currents would be biased. Thetrue diversity of foraminifera in such an inter-reefalsetting would be underestimated, and impair interpre-tations of the fossil record.
The high numerical abundance of larger benthicforaminifera (LBF) indicates that they locally con-tribute a substantial portion to the overall carbonatebudget (see also LANGERet al. 2012). These taxa con-stitute ubiquitous and prominent components of manyshallow water ecosystems and are adapted to mostlyoligotrophic conditions. Their environmental prefer-ences are close to coral reefs, making them particu-larly vulnerable to environmental/climate change oranthropogenic interference. As prominent producersof calcium carbonate, LBF foraminifera are ecosystemengineers (LANGERet al. 2012). Environmental distur-bances (e.g. pollution) are likely to perturb recipientcommunities and trigger substantial changes in eco-system functioning (e.g., changes in species diversity,carbonate production, impact on native biota; LANGERet al. 2012). Larger benthic foraminifera live in veryprecise, fragile and balanced marine environments,where even minor physical or chemical changes mayhave a significant impact on an entire coral ecosystem.With three-quarters of world reefs under threat, thecarbonate producers of reefs deserve priority attention.
5. Conclusions
Examination of sediment samples from the BazarutoArchipelago (Mozambique) indicates that foraminif-eral assemblages represent a prominent componentwithin the reefal and shallow water environments. Thehigh numerical abundance of larger benthic foraminif-era indicates that they locally contribute a substantialportion to the overall carbonate budget to the sedi-ment, and provide stability to the reef framework. Assuch, foraminifera can be considered ecosystem engi-neers. Foraminiferal assemblages occupy distinct hab-itats, and their composition is indicative of reef, chan-nel, and lagoon habitats. Hierarchical Q- and R-mode
cluster analyses reveal the presence of two groups.Clusters differ in species richness and the percentageabundances of symbiont-bearing, miliolid, aggluti-nated, and hyaline-perforate taxa. The distinct differ-ences between reef and lagoon assemblages imply lowhorizontal transport rates and favour the preservationof original assemblage structure. This observation pro-vides useful information for paleoenvironmental andpaleoecological studies of tropical reefs.
Acknowledgements
Collection and study of the material by M.L. was supportedby a grant from the German Science Foundation (DFG,LA 884/10-1). The authors gratefully acknowledge ROBERTGASTALDOfor comments on an earlier version of thismanuscript and JAN BARTHOLDYfor field and laboratoryassistance. We also thank Lopo DEVASCONCELOS(GeologyDepartment, Maputo) for logistical support and assistancein Mozambique. TOM MCCANN provided constructivecomments on the manuscript.
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Manuscript received: July 15th, 2012.Revised version accepted: September 13th, 2012.
Addresses of the authors:
MARTINR. LANGER,ANNAE. WEINMANN,JENSM. THISSEN,Steinmann-Institut fUr Geologie, Mineralogie undPalaontologie, Rheinische Friedrich-Wilhelms Universitat,Nussallee 8, 53115 Bonn, Germany;e-mail: [email protected],Egyptian Petroleum Research Institute,1 Ahmed EI-Zomor Street, EI-Zohour Region, Nasr City,Cairo 11727,Egypt.
