OCEAN 320 Lecture Notes - Lecture 3: Arlington Springs Man, Ground-Penetrating Radar, Pygmy Mammoth
Unit 3A:Ecosystems, Baselines, Fisheries
Article: The Structure of Ocean Ecosystems
• Ocean ecosystem: ratio of fish compared to elasmobranchs such as sharks, skates, rays
• Has remained stable for tens of millions of years, despite extreme environmental changes
caused by climate shifts
• Distinct shifts between three stable states occur rapidly and independent of climate shifts
• Oceanography @ UCSD: analysis of microscopic fossil fish teeth and mineralized shark
scales (known as denticles) preserved in sediments on seafloor for millions of years
o Shows there may have been two major events that substantially altered makeup of
ocean life
• Cretaceous/Palaeogene mass extinction (66 million years ago)
o Attributed with the disappearance of dinosaurs
o Abundance of fishes exploded once main predators went extinct
o Shark abundance neither rose nor fell, however
o For next 45 million years, ratio of sharks to fish remains stable; both groups
rise/fall alongside global climate change, suggests ecosystem was resilient to
climate change
• 20 million years ago: sharp drop-off in shark population, dramatic increase in variability
of fish abundance
o Suggests that sharks spend considerably less time in open ocean ecosystem
o Has to do primarily with how competition with other marine organisms (plankton,
invertebrates, sea birds, marine mammals) influenced balance of life
• Drastic swings in global climate (similar to current conditions) did little to alter the long
term structure of marine vertebrate community
o Prehistoric “episodes” do not guide potential changes in marine ecosystem today
bc rate of modern climate change is much faster than those, and impact of humans
is unprecedented
o transition from Cretaceous to Paleogene oceans: saw disappearance of highly
abundant invertebrates called ammonites
▪ mass extinction released fishes from predation and allowed population to
explode in abundance in warm greenhouse of Paleogene
o later, modern ocean system diversity (mammals, seabirds, large pelagic fish)
create competition wit sharks, which increases fish variability; this may have
driven shark abundance down
Article: Arlington Man
• Arlington Springs Man: earliest dated human remains in north and south America;
fragment of human femur discovered in 1959 tested with bone protein analysis and
radiocarbon dating; dates body back to 13,000 years ago
o Only one other find in North America; child burial in Anzick Site in Montana
find more resources at oneclass.com
find more resources at oneclass.com
• Lived at the end of the Pleistocene when all four northern Channel Islands were still
united; climate was much cooler than today
o Evidence of people there 13,000 years ago proves that watercraft were in use
along California coast; supports theory that earlier people to enter western
hemisphere may have migrated along Pacific coast from Siberia/Alaska using
boats
o Radiocarbon dating of pygmy mammoth fossils suggests the last of them may
have been present when the first humans arrives
• New technology: laser mapping, ground penetrating radar used to document the site and
gather add. info
o Most recently found series of soil cores that will yield invaluable into about
geological and environmental history of the island
Modern Oceans
• Ocean abundance was very high in Paleogene; diversity kept increasing, creature size
reaches a maximum in Modern Ocean
• By Pleistocene, oceans had cooled off; mixing was invigorated and productivity
increased
o Led to some species attaining large sizes; good example of long term bottom-up
sustinence
o Blue whale: surpasses any other Earth species in size (ever!); another large
species is the Megladon shark
o Any change in lower trophic levels would effect the big species the most
American Human History
• Early cultures integrated with seafaring and ocean subsistence
o Facilitated travel, abundance of food
• Early hunter-gatherer inhabitants resided in modern Channel Islands Natl Park, CA;
paleocoastal culture is well documented
Excerpts from Dept of Interior; Archeological Assessment Report on Channel Island Natl Park
• More than 50 archaeological sites on San Miguel, Santa Rosa, and Santa Cruz islands
have been radiocarbon dated between 13,000 and 7,000 BP
o One of largest and most significant clusters of ealy coastal sites known in
Americas
o More sites undoubtable buried beneath waves and younger dunes, alluvium, or
shellmounds
• Between 13,000 and 7,000 BP, sea levels rose about 40 meters (~130 feet) from 50 m to
10 m below modern levels
o Rising sea had dramatic effects on earliest islanders
o Describes changing climate, landscapes, vegetation, ocean resources, population,
and migration
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
); another large species is the megladon shark: any change in lower trophic levels would effect the big species the most. American human history: early cultures integrated with seafaring and ocean subsistence, facilitated travel, abundance of food, early hunter-gatherer inhabitants resided in modern channel islands natl park, ca; paleocoastal culture is well documented. Americas: more sites undoubtable buried beneath waves and younger dunes, alluvium, or shellmounds, between 13,000 and 7,000 bp, sea levels rose about 40 meters (~130 feet) from 50 m to. 10 m below modern levels: rising sea had dramatic effects on earliest islanders, describes changing climate, landscapes, vegetation, ocean resources, population, and migration. Sypnosis: early humans arrives at santa rosa island by 13,000 ypb; maybe earlier, but much of that fossil evidence washed away in ocean, evidence that they likely kept going south. Plant and animal dna suggests first americans took coastal route: plant and animal dna buried under two canadian lakes devalues theory that first.
