This course surveys the diversity, structure and functioning of California’s ecosystems through time and the ways they have influenced and responded to human activities and stewardship. Topics include ecosystem drivers such as climate, soils, and land use history; human and ecological prehistory of the state; comparative marine, freshwater, and terrestrial ecosystem dynamics; and managed ecosystems such as range, fisheries and agriculture in California. The course also emphasizes important skills to understand as a scientist or consumer of scientific information, including data collection, natural history, and writing.
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來自 University of California, Santa Cruz 的課程
Ecosystems of California
15 個評分
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與講師見面
Erika ZavaletaProfessor
Ecology and Evolutionary Biology
[MUSIC]
I'm Erika Zavaleta and this This is ecosystems of California.
Today we're visiting Ano Nuevo Island Reserve,
with reserve director, Patrick Robinson.
Thanks for having us out, Patrick.
>> Of course, I could help.
>> And Ano Nuevo Island itself is pretty small.
It's a couple of dozen acres in size, but
it's anchored to the mainland here in the much, much larger Ano Nuevo State Park.
And then of course, it's anchored to the surrounding marine ecosystems
in the sense that it's really important breeding habitat for
a variety of marine vertebrates.
It's a breeding habitat for birds like rhinoceros auklets, and
Cassin's auklets, as well as things like Western gulls and Brandt's cormorants.
And then, more famously, Año Nuevo Island and the adjacent mainland,
are important breeding areas for elephant seals, for sea lion, and
then for the steller sea loin which is a federally threatened species that finds
the Southernmost end of its breeding distribution right here at Año Nuevo.
So we're out early this morning.
Its a pretty clam morning not a lot of wind and a little bit of fog, and
you can see around us a lot of seabirds, pelicans, and gulls and
you can hear and see sea lions and elephant seals, a couple of harbor seals.
I've seen a sea otter or two, this morning.
The role that an island like this plays in the marine ecosystem is really
significant, even though it's on land and it is where all of these marine
vertebrates that we just talked about are breeding.
And so they are consuming large quantities of things like fish and
squids over huge areas of ocean and some cases like in the case of elephant seals
basically the entire pacific or a big part of it and then they are coming back and
concentrating in places like on Univo Island to reproduce.
So without these islands there wouldn't necessarily be the diversity in abundance
of marine predators that we see in a place like this.
And we're at the north end of Monterey Bay and
the Monterey Bay protected area the national sanctuary.
The Monterey Bay has been called the marine Serengeti.
It's an incredibly productive and
diverse system particularly from the point of view of marine vertebrates.
But as we'll talk about, the reason for that diversity and
abundance starts from below.
It starts with wind and
with the effects that that wind has on ocean circulation patterns around here.
By the offshore ecosystem, we're referring to the pelagic ecosystem,
everything below the surface and above the bottom of the ocean.
But as you can imagine,
there's a lot of vertical zonation happening in that water column.
[SOUND].
>> So, as we approach the island hee there are a lot of animals either roosting or
breeding.
So we see all the black dots out there are cormorants and grey ones are pelicans.
A lot of the pelicans are just roosting here.
It's one of the breeding site.
A lot cormorants are just finished their breeding season.
They're very easily disturbed animals.
That's actually why we're not going out on to the island
today just filming from the boat.
As you can see, just our presence right here has already caused
about 100 animals to take flight.
A little bit closer to the water you'll see mostly California sea lions and
some elephant seals mixed in, right now.
The California sea lions use the island mostly as just a temporary haul out.
It's a small breeding colony for the California sea lions.
I think this year we had a little over 100 sea lion births.
In the early fall there could be upwards of 10 or 12 thousand California sea
lions on the island, so it could be a pretty packed place.
Up higher on the terraces there'll be mostly adult male California sea lions.
And down lower on the beaches you'll see adult male elephant seals, and
sub adult male elephant seals.
Right now is the elephant seal molting period.
>> So the elephant seals are molting right now.
Tell us a little bit more about what that means they're doing in this
part of the year.
>> Normally they're out at sea, foraging thousands of kilometers away,
diving down to extreme depths at really cold temperatures.
And one of the reasons they can do that is because they have a really
thick blubber layer.
But that also means that they are not perfusing their skin with blood
which would cause them to lose heat.
So they do a massive repair of their fur and skin once per year.
So rather than sort of continuously shed skin like we do, they have a,
what's called a catastrophic molt., where they in the course of a week and a half or
so basically shed their entire skin and fur and regrow that.
So it's a pretty interesting thing to watch,
it looks like they have a really bad sun burn it's peeling off in giant sheets, but
that's how they manage that over the year.
So right now is the molting period for the adult males.
We just passed the molting period for the adult females and
then they'll all come together again during the breeding season in winter.
If we were to come back here in late December, we would see the adult
males start to duke it out for, not territory, but access to females.
Some species are reliant on particular physical territories like from a rock to
a rock, whereas elephant seals are really resource defense so
they will defend a group of females.
And that hierarchy gets set up fairly early on and
is maintained throughout the season through interactions between the males.
Then, shortly thereafter, in early January the adult females will arrive.
That's their fattest and most healthy course of the year for them.
They just came back from their long, foraging migration.
Eight months out at sea.
Thousands of kilometers away, feeding on fish and
squid out in the middle of the northeast Pacific.
And they're pregnant so they give birth within about a week of arriving on land
to a pup that's about 25 pounds or so.
Then shortly thereafter starts nursing.
It's a very short nursing period.
Just shy of about four weeks.
During that time the adult female is fasting, so she's not eating or
drinking but yet she's delivering gallons, and gallons of milk to that cub.
[SOUND] So that's an adult male California sea lion barking behind us there.
>> [SOUND] How much does an adult male elephant seal weigh typically?
>> They can weigh between one and two tons.
They're pretty massive.
>> It's pretty amazing to watch them move on land, move that weight around.
>> Yeah. >> [SOUND] So another way that the pelagic
marine environment and the terrestrial environment
are connected here in California is through anadromous fishes
like salmon that are moving between the places where they hatch and
live as juveniles up in fresh water creeks and rivers and streams.
And the marine environment where they spend most of their adult lives growing to
large size, being harvested by fishermen and
then being harvested by a variety of marine predators.
>> Salmon seems like a fairly strange thing to study out here.
But, it turns out, actually,
that some of the neighboring creeks, they have salmon runs in them.
And, researchers put out the little passive transponder tags,
pit tags, and a lot of those animals get eaten.
And historically they put those out there so
that they can eventually find those animals again and
they re-enter that same creek or steam but a lot of them end up here actually
because they are eaten by predators And then defecated on the island.
And so they can actually estimate rates by looking at
the frequency with which those pit tags appear on the island, so
it's kind of an interesting kind of side project that's going on out here.
>> That's really interesting.
It's kind of hard to hear out here.
It's incredibly loud.
So many sea lions barking and birds calling, and
you hear the elephant seals occasionally, with this low rumble.
And then the bird sounds pretty quiet by comparison, but
there is a fair bit of noise coming from the pelicans and gulls,
occasionally from a pigeon guillemot, with a little high-pitched call.
The bottom line, though, is that it's incredibly loud, so
you can see the numbers of animals out here, and
the collective sound they create is pretty huge.
[SOUND] Tell us Patrick a little bit about what the fate is of some of these pups and
what the role is of top marine predators like these great white sharks around
here because this is an area people talk about seeing a lot of sharks in.
>> Yeah absolutely.
Between here and the Farallon Islands,
are just really well known for the great white shark population, and
they're going after the marine mammal pups that are produced out here.
So, if you're an elephant seal born in Año Nuevo, you have about a 50% chance of
making it through your first year of life, even after you successfully wean.
So, a lot of those animals are going to feed the shark population.
And in fact the sharks are so abundant here that this where their researchers
come to put out tags on Great White sharks.
>> And they're doing that mainly on they are first out of the island in the deeper
waters.
>> Exactly, yeah.
They patrol off there waiting for the seals to leave.
Great White sharks are probably the major factor, and then a little bit farther
offshore, and up near Alaska, orcas are probably taking them as well.
>> And in some years,
we do get a number of orcas here in the Monterey Bay area as well.
Tell us a little bit about the structures on the island.
There is an old house.
There are a number of fences.
What is all that from?
>> A number of years ago, this used to be an old lighthouse station,
so this would be the type of operation that would alert ships so
that they wouldn't run aground in foggy weather.
There's a lot of shallow areas and places you wouldn't want to take a big ship here.
In fact there were a large number of ship wrecks around this area so
that's why they put the station here.
It's since been replaced by the Pigeon Point Lighthouse just
a little north of here.
You can actually barely see it through the fog there.
>> And tell us about the fences.
>> A nonprofit group by the name of has put those up
with the goal of protecting the local seabird population here.
So the problem was that the California sea lions were becoming much more abundant,
and actually walking across the nests and burrows of some of the sea birds,
and crushing them, and eliminating them as a breeding colony here.
So, in order to protect the different aquatic species that burrow,
they basically put up these habitat ridges, these walls,
that prevent sea lions from entering the area.
>> Mm-hm. >> And, as far as they can tell,
that's worked very well.
The population numbers are slowly increasing through time,
and that hasn't really hurt the sea lions out here.
They still haul out in huge numbers, so I think it's kind of a win-win,
>> The California current system
is one of the most productive marine regions in the world, and
that's because of the marine upwelling that happens here.
So you look at these large marine animals and
think about what they eat, and why there are so many of them here.
They're eating huge variety of miso predators, things like fishes and
squid, but where that all starts is with the wind here in California.
So you've got long shore winds blowing south, there equatorward along the coast.
And part of what that does is set up a southward current across the state so
that nutrient-rich cold waters are drawn up from depth.
And those nutrient-packed waters form the base of the food web that supports these
huge marine vertebrates in these huge numbers.
So we've got that upwelling.
The upwelling in turn supports phytoplankton, diatoms,
dinoflagellates and cyanobacteria, and as phytoplankton are photosynthesizing.
So they're using sunlight to produce all of the calories and energy that flow up
from there into first zooplankton including things like euphausiids, krill,
that are consumed by fishes by a whole variety of seabirds and marine animals and
all the way on up to the largest animals in the world, the baleen whales.
And they you get to these pinnipeds, and killer whales and
sharks that are eating large marine organisms.
So the marine food web is really complex.
It's really rich, and ultimately it's undergirded here.
This incredible productivity by the wind.
>> So I did my PhD work at Ana Nuevo here, working on the northern elephant seals,
particularly their at sea behavior.
I was focused on a couple different aspects of their behavior.
One was their foraging behavior, basically how do they go out and
And make a living out in the open-ocean environment.
How do they find their prey resources out there, and
how successful are they when they do that, so,
for that, we had to track where the animals are going, how deep their diving.
So we literally tagged hundreds of northern elephant
seals by attaching satellite tags and climb depth recorders.
We attached those instruments to known individuals and
then watched where they went and how they were diving over their
long forging migrations, and they have a really interesting behavior.
They're at sea continuously, they never actually sleep for long periods like we're
normally used to but they do have a behavior called a drift dive.
It's at the end of a full night of foraging,
they'll have a bout of two to five drift dives and
this means they swim down to about 200 meters, which is pretty shallow for them.
But then just passively drift through the water columns spiraling down to
about 600 meters.
And we think that they might be sleeping, certainly processing food from
the last night's meal and what's very interesting about their behavior once they
start swimming again at the bottom of those dives is that they can successfully
reorient themselves back on the same trajectory they were going at previously.
So they're able to maintain these very straight transit courses over thousands
of kilometers for weeks on end despite not having any cues available to them or
seemingly cues that we would be able to use to navigate.
And so they are able to go out into the middle of the northeast pacific and
back two times per year.
>> Mm-hm.
>> Very accurately and always find their way back to Ana Nuevo.
Maybe not always but most of the time.
>> Did you get any sense of how?
>> We don't know for sure.
I was mostly focused on looking on how accurately they can navigate,
but we think we've narrowed it down to a couple of different options
using the earths geomagnetic field.
>> Mm-hm. >> Or
possibly very low frequency of sounds, infraound.
We think they're not using celestial cues which is thought to be
occurring for a long time.
>> And they're not using visual cues in general if they're able to do it
where it's dark, that deep below the surface.
>> Exactly.
Day or night, thousands of kilometers away from the coast there's no stable visual
cues for them.
They're not reaching the bottom of the ocean.
There's no mountains or anything they can see off in the distance.
So they have to have some trick up their sleeve to do that.
>> Amazing.
[MUSIC]
