Northern Hemisphere Kelp Forests

[Tassie_Rohan]

Over the past 20 years or so have the kelp forests in northern waters died off at all?

Down here in Tasmania the kelp forests have been disappearing over the last 10 years with around 90 % of the forests I remember diving on in the late 80's now gone.

Many factors have been blamed: a change from a cold water current from the south to a warm water current from the north (unproven?), small scale commercial farming of kelp and the overfishing of lobster (crayfish) allowing a sea urchin population boom- which apparently damage the kelp anchors.

I’m curious to know if the kelp forests are also dieing off in northern waters – and if so why? Is this a local or global phenomenon?

Cheers,
Rohan.

 

[archman]

Dr.Bill probably knows more about California kelps than anyone else on the board, or the world for that matter. I'm sure he'll pipe in soon.

I haven't heard about any declines in kelp off western north america, personally. Not any serious ones, anyway.

 

[kelpmermaid]

You might find some of this interesting, though.

http://www.ccd.org/research/reports/reports.html

 

[archman]

You might find some of this interesting, though.

http://www.ccd.org/research/reports/reports.html

Huh.. I didn't know California had a diadema-type urchin. How fancy!

 

[Tassie_Rohan]

Thanks for the link Kelpmermaid: those papers were exactly the sort of stuff I was after. They tie in the link between elevated water temperatures and kelp die offs pretty succinctly (especially during the el nino years), and its interesting to see that the urchin population remained constant: When diving locations where there were once kelp forests you tend to see 1000's of urchins and come to the conclusion that they were responsible, when the apparent increase in abundance may just reflect lest cover for them to hide in.

The big question I guess is are the kelp die offs down here due to on one-off el nino events switching currents around, or does it reflect that much abused term ‘global warming’. Looks like I'll have to do a bit more research on kelp forest ecology and ocean temperatures…

Cheers,
Rohan.

 

[kelpmermaid]

Another thing of interest is this:

http://www.cacoastkeeper.org/current-programs.html

A member on this board, Kelphelper, participates in this program. Somewhere on the web I recall seeing aerial photos of the CA coast (and maybe Catalina?) before and after an El Nino event, and the change in visible kelp beds was substantial.

 

[drbill]

I have a few of my research papers on my web site (see link below, look in scientific research section) that talk about "long-term" changes in kelp forests here. We had a "long-term" warming trend that initiated in abot 1976-77 that really seemed to decimate the kelp in the warmer sections of Catalina (Long Point to the East End primarily). Superimpose on that the El Nino fluctuations.

During warmer water (like the 82-83 El Nino event) echinoderms often succumb to pathogens here, so their numbers may actually decrease. In areas where sheephead and other predators are abundant (like the Casino Pt. park), they keep the urchins in check. Further north in the northern Channel Islands there are few sheephead left due to overfishing and there are urchin barrens present.

Dr. Bill