Tuesday, June 4, 2019

Mar­ine Eco­sys­tems Have Entered the An­thro­po­cene, According to Fossil Zooplankton

Cli­mate change caused by hu­mans im­pacts spe­cies di­versity and eco­sys­tems, and mar­ine eco­sys­tems are no ex­cep­tion. In or­der to as­sess ex­actly how cli­mate change af­fects eco­sys­tems, their cur­rent state has to be com­pared with the situ­ation be­fore hu­man in­flu­ence.

The spe­cies com­pos­i­tion of plank­tonic fo­raminifera from the past is stored in the sed­i­ments.
The species composition of planktonic foraminifera from the past is stored in the sediments. Photo: MARUM - Center for Marine Environmental Sciences, Univeristy of Bremen; M. Kucera
 Photo: MARUM - Cen­ter for Mar­ine En­vir­on­mental Sci­ences, Uni­v­eristy of Bre­men; M. Ku­cera

 Re­search­ers from MARUM – Cen­ter for Mar­ine En­vir­on­mental Sci­ences of the Uni­versity of Bre­men, and from the In­sti­tute for Chem­istry and Bio­logy of the Mar­ine En­vir­on­ment at the Uni­versity of Olden­burg, have now shown that the as­so­ci­ations of mar­ine plank­ton in the present are markedly dif­fer­ent from those of pre-in­dus­trial times. It can be said that mar­ine plank­ton has now entered the An­thro­po­cene epoch. The re­search­ers com­pared the com­pos­i­tions of fossil plank­ton (fo­raminifera) as­semblages in sed­i­ments of the pre-in­dus­trial era with those of more re­cent times. The team has pub­lished their res­ults in the journal Nature.

Plank­tonic fo­raminifera are mi­cro­scopic or­gan­isms that live in the sur­face wa­ters of the oceans. When they die their cal­careous shells are de­pos­ited in the sea­floor sed­i­ments. These fossil fo­raminifera doc­u­ment the spe­cies com­munit­ies be­fore hu­mans began to al­ter the Earth’s cli­mate. In turn, in­form­a­tion on the present-day state of plank­tonic fo­raminifera is re­vealed by samples col­lec­ted in sed­i­ment traps over the past 50 years. By com­par­ing the fossil and mod­ern com­munit­ies of fo­raminifera, re­search­ers can de­term­ine to what ex­tent the plank­ton as­semblages have changed since the be­gin­ning of in­dus­tri­al­iz­a­tion.

For their study, Dr. Lu­kas Jonkers and Prof. Michal Ku­cera of MARUM at the Uni­versity of Bre­men, and Prof. Helmut Hil­l­eb­rand of the In­sti­tute for Chem­istry and Bio­logy of the Mar­ine En­vir­on­ment (ICBM) at the Uni­versity of Olden­burg, com­pared over 3,700 samples from pre-in­dus­trial sed­i­ments with samples from sed­i­ment traps that re­flect the plank­ton status from 1978 to 2013. The sci­ent­ists have con­cluded that the present-day spe­cies com­munit­ies are sys­tem­at­ic­ally dif­fer­ent from pre-in­dus­trial times. “The ex­cit­ing res­ult was that this dif­fer­ence is not ac­ci­dental, rather it re­flects a sig­nal of global warm­ing. Mod­ern com­munit­ies in areas that are be­com­ing warmer are sim­ilar to pre-in­dus­trial com­munit­ies from warmer re­gions, in­dic­at­ing that spe­cies com­munit­ies have shif­ted their dis­tri­bu­tion in a dir­ec­tion con­sist­ent with tem­per­at­ure change,” ex­plains Lu­kas Jonkers.

“We have known for a long time that spe­cies as­so­ci­ations are chan­ging, but for many bio­lo­gical com­munit­ies there were no re­li­able bench­marks, par­tic­u­larly on a global scale, due to the short time dur­a­tion of ob­ser­va­tions," says Jonkers. This has now changed with the data ana­lyzed by these work­ers. “The data set is very large and also glob­ally rep­res­ent­at­ive.” The dis­turb­ing as­pect of the ob­ser­va­tion is that in many re­gions of the ocean the plank­ton com­munit­ies have evid­ently mi­grated "into alien wa­ters". There they must ad­apt to new con­di­tions and, in some cases, re­build their food webs. “The ques­tion is whether they can do this rap­idly enough, or whether cli­mate change will pro­gress faster than the com­munit­ies can ad­apt,” says Michal Ku­cera.

“Our co­oper­a­tion il­lus­trates how im­port­ant it is for pa­leoe­co­logy and mod­ern biod­iversity re­search to work to­gether,” adds Helmut Hil­l­eb­rand. He is the head of the plank­to­logy work­ing group of the ICBM and of the Helm­holz In­sti­tute for Func­tional Mar­ine Biod­iversity at the Uni­versity of Olden­burg. “Our study helps to un­der­stand how cli­mate change im­pacts biod­iversity. This is one of the prom­in­ent ques­tions in the latest global re­port by the In­ter­gov­ern­mental Sci­ence-Policy Plat­form on Biod­iversity and Eco­sys­tem Ser­vices (IPBES).

The re­ac­tion of mar­ine eco­sys­tems to cli­mate change is an on­go­ing topic of re­search by sci­ent­ists in Olden­burg and Bre­men within the Cluster of Ex­cel­lence “The Ocean Floor – Earth’s Un­charted In­ter­face.”

Contacts and sources:
Dr. Lu­kas Jonkers
MARUM - Center for Marine Environmental Sciences, University of Bremen

Citation: Global change drives modern plankton communities away from the pre-industrial state
Lukas Jonkers, Helmut Hillebrand, Michal Kucera. Nature, 2019; DOI: 10.1038/s41586-019-1230-3

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