Responses of macrobenthic communities to patchy distributions of heavy metals and petroleum hydrocarbons in sediments:A study in China's Zhoushan Archipelago

This study conducted four cruises during 2014–2017 to investigate relationships between macrobenthic communities and sediment contaminations in sea area around the Zhoushan Archipelago.Fourteen sites were categorized into three groups:high total heavy metal contamination content(HHMC),high total petroleum hydrocarbon content(HTPH),and low content ratio of heavy metal contamination content to total petroleum hydrocarbon content(HMC/TPH)areas.Four main taxa of macrofauna(polychaetes,bivalves,gastropods,and crustaceans)were determined to respond to environmental factors differently.While tolerant polychaetes being the minimal impact by environmental factors,bivalves were threated by heavy metal pollutions in sediment.Additionally,body size distribution frequency demonstrated that macrofauna in the low HMC/TPH areas were less disturbed by contamination than those in the HHMC and HTPH areas.The result represented the presentation of sensitive species while tolerant species are usually considered as small size organisms.Overall,this study confirmed the hypothesis that the contamination levels of small-scale patches is indicated by the condition of macrobenthic communities.

Discovery of Cladonema multiramosum sp.nov.(Cnidaria:Hydrozoa:Cladonematidae)using DNA barcoding and life cycle analyses

In contrast to typical planktonic hydromedusae,Cladonema medusae are mostly benthic,with specialised adhesive branches to adhere to the substrate.In this study,a Cladonema species discovered in a laboratory aquarium in Fuzhou,China,was confirmed as a new species,based on morphological and molecular analyses.The species was named Cladonema multiramosum sp.nov.Its medusa is distinct from that of congeners possessing substantially more adhesive branches(8-24,rarely 5-7),and tiny branches on the upper radial canals.The validity of C.multiramosumum sp.nov.was also supported by molecular phylogenetic analyses based on the mitochondrial 16S rDNA sequence.However,C.multiramosum sp.nov.medusa also displayed considerable phenotypic plasticity with respect to its radial canals,tentacles,stinging branches per tentacle,oral tentacles,manubrium,and gonads,hindering species identification based solely on morphology.Although some morphological characteristics of hydroids(filiform tentacles and medusa buds)and nematocysts could also be used as diagnostic characters in the genus Cladonema,this information is unavailable for some Cladonema species.Thus,the taxonomy within the genus Cladonema was re-evaluated based mainly on the morphological characteristics of the medusa.Further revision of the genus Cladonema should be made when supplementary information on the life cycle and DNA barcoding are updated.