Response of coralline algae Porolithon onkodes to elevated seawater temperature and reduced pH

Coralline algae(CA),a type of primary calcifying producer presented in coastal ecosystems,are considered one of the highly sensitive organisms to marine environmental change.However,experimental studies on coralline algae responses to elevated seawater temperature and reduced pH have documented either contradictory or opposite results.In this study,we analysed the growth and physiological responses of coralline algae Porolithon onkodes to the elevated temperature(30.8°C)and reduced pH(7.8).The aim of this analysis was to observe the direct and combined effects,while elucidating the growth and photosynthesis in this response.It was demonstrated that the algae thallus growth rate and photosynthesis under elevated temperature were depressed by 21.5%and 14.9%respectively.High pCO2 enhanced the growth and photosynthesis of the thallus at ambient temperature,while they were deceased when both temperature and pCO2 were elevated.CA is among the most sensitive organisms to ocean acidification(OA)because of their precipitate high Mg-calcite.We hypothesize that coralline algae could increase their calcification rate in order to counteract the effects of moderate acidification,but offset by the effect of elevated temperature.Accordingly,our results also support the conclusion that global warming(GW)is a stronger threat to algal performance than OA.Our findings are also proposed that coralline algae may be more resilient under OA than GW.

Detail description of Lithophyllum okamurae(Lithophylloideae,Corallinales), a widely distributed crustose coralline alga in marine ecosystems

Lithophyllum okamurae is one of the important encrusting coralline algae,which plays important roles as primary producer,carbonate sediment builder,and habitat provider in the marine ecosystems.In this study,L.okamurae was collected from tropical coast of Sanya,and firstly described based on both detailed morph-anatomical characteristics and molecular studies of typic DNA sequences.The structure of the thalli of L.okamurae was pseudoparenchymatous construction with radially organized dimerous organizations in the crustose portion.The pseudoparenchymatous construction were composed of three parts,including 1 to 3 layers of epithelia cells which had flatten to round outermost walls,one layer of square or rectangular cells of the hypothallia and multiple layers of square or elongated rectangular peripheral cells.Palisade cells were observed,and the cells of the contiguous vegetative filaments were connected by secondary pit-connections with cell fusions absent.The carposporangial conceptacles,the spermatangial conceptacles,the bisporangial conceptacles and the tetrasporangial conceptacles were observed,and all these four kinds of conceptacles were uniporate.The spermatangial conceptacles were slightly convex and buried at shallow depths in the thalli tissues,and the carposporangial conceptacles and asexual conceptacles were protruding and conical.Phylogenetic studies based on DNA barcoding markers of 18 S rDNA,COI,rbc L and psb A revealed that L.okamurae clustered with the closest relation of L.atlanticum,and formed a distinct branch.Based on the comparative anatomical features and the molecular data,the detailed description of the valid species of L.okamurae was firstly given in this study to provide theoretical basis for algae resources utilization and conservation in marine ecosystems.

Six Thallus Surface Types of Coralline Algae with Descriptions of Two New Records of Amphiroa beauvoisii and Neogoniolithon setchellii in Sanya reef,China

Coralline algae are globally distributed calcifying species and play critical ecological roles to marine ecosystems by contributing significantly to their structural complexity and diversity.Thallus surface types of historical samples in Sanya coral reef reserve were studied based on the scanning electron microscope(SEM)method.Our results show six thallus surface types within the study area:Corallina-type,Jania-type,Leptophytum-type,Phymatolithon-type,Pneophyllum-type,and Spongites-type.The Phymatolithon-type is the dominant surface type in Sanya reefs.Two new record species in the region are described:Amphiroa beauvoisii and Neogoniolithon setchellii.Although thallus surface types provide useful diagnostics characters for distinguishing coralline algae at tribe or subfamily level,species identification needs to refer to the reproductive features.This is the first surface study of coralline algae in the South China Sea.This result provides the baseline data needed for the monitoring and management of reef-building organisms of coral reef in China.

Diversity of Middle Eocene Coralline Red Algae from the Prang Limestone(Shella Formation) of Jaintia Hills, Meghalaya, NE Himalaya, India with special emphasis on palaeoenvironment

Palaeocene-Eocene carbonates of shallow marine sequence belonging to Shella Formation of Jaintia Group are well developed in the south of the Jaintia Hills, Meghalaya and represent an excellent outcrop of shelf sediments in North Eastern Himalaya, India. These outcrops are exposed along the southern fringe of Shillong Plateau. The Prang Limestone is the uppermost lithostratigraphic unit of the Shella Formation within the Jaintia Group. It is overlain by sand-shale alternation of the Kopili Formation and underlain by the Narpuh Sandstone. A rich assemblage of larger foraminifera including Nummulites, Discocyclina etc. has been recorded earlier from the Prang Limestone and based on the foraminiferal assemblage, a Middle Eocene to Early Late Eocene age has been assigned to the Prang Limestone. Thin section analysis of the Prang Limestone revealed the abundance of well preserved coralline red algae along with other well preserved and significant biogenic elements. Morpho-taxonomical study reveals that the algal flora is represented by seven species belonging to the families Hapalidiaceae(Subfamily: Melobesioideae), Corallinaceae(Subfamily: Mastophoroideae) and Sporolithaceae. The dominance of melobesioid and mastophoroid forms is the characteristic feature of this algal assemblage. Coralline algae occur mostly in encrusting growth form with orbitoid foraminifera and occasionally the coralline algae form rhodoliths. On this basis of algal forms it can be inferred that they thrived in a shallow, warm, shelf environment of normal salinity.

Facies analysis and paleoenvironmental interpretation of Piacenzian carbonate deposits from the Guitar Formation of Car Nicobar Island,India

Facies characterization of Piacenzian （late Pliocene） carbonate sediments of the Guitar Formation in Car Nicobar Island,India and the subsequent integration of paleoecological data have been applied to interpret the paleoenvironment of the coralline algal-reef deposits.Thin-section analysis reveals that Amphiroa,Corallina and Jania are the dominant geniculate corallines,while Lithothamnion,Mesophyllum,Phymatolithon,Lithophyllum,Spongites and Lithoporella are the major non-geniculate corallines contributing to the sedimentary facies.Numerous small and larger benthic foraminifera also dominate the biogenic assemblages.Corals,barnacle shells,echinoid spines,fragments of bryozoans,mollusks and ostracodes are the subordinate constituents.Grainstones dominate the studied facies while packstones and boundstones （with wackestone elements） are the sub lithofacies showing a fair representation.Six carbonate facies presenting a complete reef complex have been distinguished that were deposited in shallow intertidal,back-reef shelf/lagoon,reef and deeper fore-reef shelf settings.Evidences of coralline algal and benthic foraminiferal assemblages,taphonomic signatures of abrasion and fragmentation,grain size,angularity and encrustation indicate a shallow to relatively deeper bathymetric horizon of approximately 10-60 m that corresponds to a regime of high to moderate hydrodynamic conditions.