As the Tides Go By

A quick update on our newest staff members: Nate and Laura are now happy as two little urchins in a kelp forest. They are settled in and really getting to know (or re-know as the case may be) all the critters and are confidently sharing the secrets of the sea with our guests. Unfortunately, their education will be taking both of them back to Victoria in early September.

Nate is startled by the hefty size of the Horse Clam (above) and is pleased with jello-like consistency of the California Sea Cucumber. [Mary Vasey]

These past weeks have been ones of high highs and low lows- with the tides of course. Such low tides are a great opportunity for the aquarium staff to replenish the intertidal tanks. One of the items at the top of our wish list was the always-impressive geoduck. When you want to find a geoduck you have to think like a geoduck so that is just what Laura, Dave, and Caylan did. They were roaring to go at 630 in the morning during the low-tides and made their way to Tofino mudflats. Because geoducks have such long siphons they are able to live very deep under the squishy sand making them difficult to dig up even with snowshoes, shovels, and cross country skis. Their siphons are full of the water that they are filtering and they are able to release this water by squirting it out of the sand and this is how a geoduck's location can be spotted. It is illegal to harvest any sort of mollusk or shellfish in many areas due to contamination (poo!) and/or Paralytic Shellfish Poisoning (PSP). The DFO website has regional updates about the coastline and which areas are legal harvest areas.

Laura (left) and Caylan (right) try to maintain their balance as they show off their victory geoducks. [Dave Hurwitz]

Red tide is harmful because of the natural dinoflagellate biotoxin saxitoxin and this chemical can prove fatal for humans even in doses as low as 0.2 milligrams. Often the affects of red tide from direct water consumption is negligible as the saxitoxin is not concentrated enough. This is not the case, however, when dealing with filter-feeding mollusks that condense the toxins within their biomass. It is this accumulation of saxitoxin that makes shellfish poisonous sometimes even years after the dinoflagellate outbreak has cleared. The symptoms of consuming affected shellfish becomes apparent within 2-12 hours of eating and include dizziness, diarrhea, vomiting, disorientation, eye irritation, and death. Due to the intense toxicity of saxitoxin it is one of only two natural toxins that are classified as Schedule 1 Chemical Warfare Agents and are considered a Biological Weapon.

Laura gives the thumbs-up after checking the DFO website for geoduck and shellfish closures. [Caylan Piper]

The lethal nature of this toxin comes from its ability to block sodium-channels with extreme selectivity and potency while leaving potassium and calcium channels unharmed. These channels are all part of our intricate nervous systems and medical research using saxitoxin has lead to a better understanding of how nerves and their channels work. (Edwards, Neil. 1998. http://chm.bris.ac.uk/motm/stx/saxi.htm)

Dave-the-master-clam-digger holds up a frightened geoduck releasing water. [Laura Griffith-Cochrane]

Rocky intertidal collections were also possible during these times of low tides and were executed by Spencer, Dave, Mary, and our volunteer Jordan from Parks Canada. Scoping out our secret spots during these few morning opportunities proved fruitful. Sea urchins were particularly abundant during our recent adventures as evident in our newest tank design. When found in tide pools, purple sea urchins are found hiding in perfectly-fitting dug outs. The reason these holes are so snug is because the urchins are actually creating them as they grow larger. They use their calcite teeth to dig into rock (often limestone) even though the rocks can be of equal or greater hardness. This is possible because the urchin's five teeth also contain crystallized magnesium calcite which is a little bit harder. There is more magnesium calcite in the tip of the tooth and it is aligned in such a way that as the teeth get ground down the interwoven crystals break in a manner that continues to create a sharp point. (Live Science. 2009. http://www.livescience.com/animals/090514-sea-urchin-teeth.html)

One last photo shoot for these collected shore crab before they are put in the octopus tanks for breakfast. [Caylan Piper]

The boys are stoked on their beach-combing prizes. [Mary Vasey]

-Mary Vasey, Interpreter