Ocean currents move ocean animals around.

Small animals in the ocean can be pushed around by currents, and may not be able to choose where to go. Adult fish and mammals can swim strongly, and adultinvertebrates cling to the bottom, but babies are at themercy of the currents.

Juvenile Shortbelly Rockfish

Adult China Rockfish

Mary Nishimoto and Libe Washburn (UCSB), June 1998

Mary was interested in rockfish, hadn’t found anyLibe saw a strong counter-clockwise eddy, 30 km acrossSurface currents up to 0.4 m/s Eddy shows in sea surface temperature imageAll the fish were in the eddy

Following year, eddy was weaker and moved aroundNo high concentration of fish

1998 1999

Summer 1998Closed eddy, lots of fish

Summer 1999Open eddy, fewer fish

Currents averaged May 1 – June 15 each year

Standard ecological theory (land):Animals are found in comfortable environments

Marine ecological theory:Animals may be found where the currents put them.Depends on animals lifestyle.

Life styles in the ocean:

1. Drifting – planktonic/pelagic2. Swimming - nektonic3. Attached - benthic

Planktonic – passively drifting or weakly swimming organisms moved by ocean currents; include bacteria, phytoplankton,

zooplankton

Pelagic – of the open ocean, not site attached

1. DRIFTERS

Jellyfish, comb jellies, heteropods, pteropods, salps

0.2 cm 70 cm

5 cm

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organisms that swim actively in open water, independent of water currents.

2. Swimmers

Benthic – ‘site’ attached, living attached to or on the ocean floor

3. ‘Attached’ organisms

Many marine species have ‘bipartite’ life histories

1. Planktonic dispersive early stage

2. benthic or site attached adult stage

BENTHIC ADULTS

REPRODUCTION

SETTLEMENT

PLANKTONICLARVAE

*Larva: an independent, often free-living, developmental stage that undergoes changes in form and size to mature into the adult; especially common in insects and aquatic organisms. (From a Latin word meaning "ghost" or "mask.")

More facts of nature: you don’t see the bipartite lifestyle often on land

Why is a bipartite life history interesting?

For most marine species, we have NO idea where larvae go

Take-home points:

• multiple life styles

• most commonly, larvae are different from adults (bipartite life history)

• do the larvae move to new adult habitats? (open population)

Larval Transport on Ocean Currents:

• Determines where and when larval settle and become adults.• Affects where and when a given species is found.

An example from the Oregon Coast …

Wind from the North, drives upwellingEkman transport pushes water offshoreVery few barnacles settle in intertidal

A few days later …

Wind relaxes or blows from SouthEkman transport pushes water onshoreLots of barnacles settle in intertidal

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DispersingLarvae

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Cluster around Point Conception For dispersing larvae only

The PISCO Project

Biogeographic Representation

Transition

Oregonian

Californian

Onshore Monitoring – Onshore Monitoring – RecruitmentRecruitment

Examples of recruitment collectors

Late summer recruiter, 1997-1999

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Average surface currents: 15 Jul 99

poleward

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Tricolia sp.Winter recruiter, 1997-1999

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poleward

Review:Currents affect the spatial patterns of larval settlement.

Leptopectin (a scallop) spawns in late summerLarvae are affected by convergent circulation at Pt CSettlement is high only inside the SB Channel

Tricolia (a snail) spawns in winterLarvae are affected by poleward circulation at Pt CSettlement is high inside and outside SB Channel

These patterns make sense if all the larvae are spawned in SBC

Larval Transport on Ocean Currents:

• Determines where larval settle and become adults.• Affects where a given species is found. •Connects different habitats.

Animals born in one place may spend their adult lives in another.If you want to protect a species by creating a safe haven (nofishing), do you choose its larval or adult habitat? BIG question in design of marine reserves.

Review: Ocean currents affect where animals are found

Rockfish study in Santa Barbara Channel: • Juveniles gathered in strong eddy 1998• Weaker eddy in 1999 did not result in high concentration• Did currents affect fish directly or by concentrating food?

Effect of currents depends on lifestyle:• Swimmers can go where they please• Animals and plants attached to bottom can resist currents• Drifters float on currents

Many marine animals have bipartate lifestyle.Larval stage drifts, adults swim or attach to bottom.

Drifting of larval stages may determine where some species are found

Marine organisms respondto currents as well as habitat quality (like temperature or salinity).

Organisms on land respond only to habitat.

The organisms:

Inter-tidal invertebrates: ( mussels, barnacles, crabs, …)- planktonic phase from hours to months- size: ~ 1 mm- weakly swimming or non-swimming- larvae may change vertical position in water column

Fishes: (juvenile rockfishes and hake, lamp fishes, smooth tongue)- larval/juvenile stages: weeks to months- size: ~ few to several cm- swimming speeds: ~ few cm/s - daily vertical migrations: up to 100’s of m

Nearshore Moorings - Nearshore Moorings - DesignDesign

TemperatureRecorder

Current Meter

Floats

Collectors (4 Types)

Fluorometer

Take-home points:

• multiple life styles

• most commonly, larvae are different from adults (bipartite life history)

• do the larvae move to new adult habitats? (open population)

• implications for marine reserve design