Dive Dry with Dr. Bill

#689: Signs of Life

Many years ago a high school friend of mine (Susie Hoover Basak) sent me an announcement of the birth of her first child. On it was a baby's footprint with the words "A child is God's way of saying that the world should go on." That has stuck with me over the decades. Of course that baby is now a 37-year old father of three children himself.

Rebirth is part of the on-going eco-evolutionary spiral that I taught my students about back in my Toyon era. Our current ecological state in Catalina's kelp forests is a sad one, but it is just a slice in time for these ecosystems. Through time life ceases and new life begins. Through time changes occur in the environment. Through time species evolve and adapt to these changes. Of course I hope the changes involve a return to healthy giant kelp communities.

Although still quite warm for this time of year, our local waters have cooled down below the 68° F threshold where giant kelp (Macrocystis pyrifera) physiology can begin normal growth. The Asian invader or devil weed (Sargassum horneri) is still impacting giant kelp's ability to develop in our dive park, but it is slowly dying out.

I've reported that a somewhat healthy stand of giant kelp has persisted near the harbor end of the park over the past two years. Cold water from the depths off the harbor entrance has been periodically brought up by winds from the southeast allowing the kelp there to utilize its nutrients and survive.

However, during the previous two years much of that kelp has not been able to grow once the fronds reach the warmer surface waters. The tips of the fronds exhibit a lack of growth with blades dying off (or eaten by ravenous herbivorous fish) and the float bulbs or pneumatocysts deteriorating. No Macrocystis canopy has formed in the park for a long time. Heck, I barely remember what it is like to dive beneath it (but can remember distinctly things I did when I was five years old... hmmm).

On one of my dives back in February I was pleased to see signs of new life. Some kelp "plants" had emerged through holes in the dense devil weed and more should follow as that invader dies off in its annual cycle... assuming water temperatures don't warm up too much as summer approaches.

There were also many indications that kelp was producing new fronds closer to the bottom. Giant kelp is a perennial with its holdfasts surviving several years assuming storms don't detach them or extremely warm temperatures don't kill them. New growth begins from the holdfast near the base and new fronds begin their journey to the surface to capture sunlight for photosynthesis.

A frond refers to a stipe (or "stem") with all its blades ("leaves"). At the tip of a healthy frond one should find the region of growth known as an apical meristem. Here the last blade can be seen splitting into many new blades, which is the process by which the kelp continually renews itself.

Apical meristems are quite beautiful structures in themselves. The Monterey Bay Aquarium uses one as part of its logo. Underwater photographers often take many images to capture the perfect still to frame for their walls (I'm still trying).

When I see these apical meristems developing, I have new faith in the continuation of life in our kelp forests. Under proper conditions the meristem may grow about a foot a day, and under ideal conditions possibly two feet a day. That growth not only enhances the health of the kelp itself, but eventually provides one of the bases for the food webs that keep other kelp forest species alive and kicking. It also makes kelp forest ecologists like myself happy campers. So here's to new life... and hope for the future.

© 2016 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Healthy kelp fronds and nutrient starved ones with Sargassum in background;
apical meristems showing growth through splitting of the terminal blade.

This document maintained by Dr. Bill Bushing.
Material and images © 2016 Star Thrower Educational Multimedia