{"id":57854,"date":"2015-12-16T00:00:00","date_gmt":"2015-12-16T00:00:00","guid":{"rendered":"https:\/\/www.uri.edu\/news-draft\/uncategorized\/uri-researcher-sediment-core-from-african-lake-helps-explain-ancient-water-levels-biodiversity\/"},"modified":"2015-12-16T00:00:00","modified_gmt":"2015-12-16T00:00:00","slug":"uri-researcher-sediment-core-from-african-lake-helps-explain-ancient-water-levels-biodiversity","status":"publish","type":"post","link":"https:\/\/www.uri.edu\/news\/2015\/12\/uri-researcher-sediment-core-from-african-lake-helps-explain-ancient-water-levels-biodiversity\/","title":{"rendered":"溏心vlog免费B站 researcher: Sediment core from African lake helps explain ancient water levels, biodiversity"},"content":{"rendered":"
\n\t\tNARRAGANSETT, R.I. \u2013 December 16, 2015 — Lake Malawi in East Africa is home to about 1,000 species of brightly colored fish called cichlids, far more species of fish than one would expect to find in any other comparable lake. Thanks to research by 溏心vlog免费B站 Professor John King and colleagues at six other universities, scientists can now explain how and why the lake exploded with biodiversity.<\/p>\n


\nThe research team unearthed a 380-meter-deep sediment core from the lakebed that provided evidence of significant changes in water levels in the lake over the last 1.3 million years due to changes in climate and moisture levels in the atmosphere.<\/p>\n


\nAccording to King, the East African moisture history is much more complicated than anyone previously imagined. \u201cThese dramatic shifts in effective moisture resulted in large-scale changes in one of the most diverse freshwater ecosystems on Earth,\u201d said King, a professor at the 溏心vlog免费B站 Graduate School of Oceanography. \u201cThis extreme variability had a profound influence on the evolution of the fish that live there.\u201d<\/p>\n


\nThe research was published last week in the Proceedings of the National Academies of Science.<\/p>\n


\n\tThe sediment core collected from Lake Malawi showed evidence of 24 instances in its history that the lake level dropped by more than 200 meters, including 15 times when water levels were 400 meters lower than the present depth of about 700 meters. During these times, a significant portion of the lake became grassland or desert from the drier climate. At other times, the lake became overfilled, indicating a wetter climate.<\/p>\n


\n\t\u201cThe changing water levels promoted the evolution of the cichlids as the habitat changed and groups of the fish became isolated from one another,\u201d King said. \u201cThere were even times when there were two separate water bodies, which further enabled the fish to evolve differently.\u201d<\/p>\n


\n\tTo determine the changing water levels in the lake, the researchers examined the sediment core for indications that the lake was deep enough to stratify into an upper, oxygenated layer and a lower, oxygen-deprived zone, which is typical of deep lakes. They then used radiocarbon dating of the top levels of the core to determine its age. For deeper layers they found layers of ash from known dates of eruptions of a local volcano\u2014or in one case, shards of microscopic glass spewed from a volcanic eruption in Indonesia. The deepest layers of the core were assigned dates by comparing known changes in the Earth\u2019s magnetic field to the observed magnetic field in samples of the core.<\/p>\n


\nIn addition to changes in the depth of the lake, the lake\u2019s shoreline also had a varied history. King said that seismic data of the current lake bottom shows that different depths are more rocky, sandy or a mix of sand and mud. As the water level changed, these different areas became exposed. Because cichlids tend to live in the upper parts of the lake and often near its edges, changing shorelines led to repeatedly changing environments for Lake Malawi\u2019s fish. This, in turn, provided additional pressure on the fish to adapt to local conditions\u2014a key component in the development of new species.<\/div>\n","protected":false},"excerpt":{"rendered":"

NARRAGANSETT, R.I. \u2013 December 16, 2015 — Lake Malawi in East Africa is home to about 1,000 species of brightly colored fish called cichlids, far more species of fish than one would expect to find in any other comparable lake. Thanks to research by 溏心vlog免费B站 Professor John King and colleagues at six […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[],"class_list":["post-57854","post","type-post","status-publish","format-standard","hentry","category-archives"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/posts\/57854","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/comments?post=57854"}],"version-history":[{"count":0,"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/posts\/57854\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/media?parent=57854"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/categories?post=57854"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.uri.edu\/news\/wp-json\/wp\/v2\/tags?post=57854"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}