On August 10, 2015, Vancouver Aquarium scientist Jeff Marliave videotaped damage occurring to glass sponges off the coast of Bowen Island in Howe Sound. In sponge gardens (cloud sponges growing on rock surfaces) some of the shallowest occurrences of cloud sponges are where the earliest signs of damage by warming seas can be detected. The sponges in the photo above occur at about 18 metres depth.

Vancouver Aquarium Howe Sound Research

Temperature logger being inserted into dead portion of a head of cloud sponges in shallow water.

Our shallowest study site for these glass sponges is near Bowen Island at a depth of about 15 metres. On August 28, Aquarium research technician Laura Borden placed a temperature logger provided by citizen scientist Glen Dennison of the Underwater Council of B.C. into dead tissues of a large sponge at this shallow site. The dead tissue resulted from past damage by the 2009/2010 El Niño, but some portions of tissue recovered into healthy new growths during the ensuing La Niña years. Now that an El Niño is building, signs of tissue stress are evident in these new sponge growths at that site, so the temperature logger was installed to give a complete record of temperatures that may prove fatal to these delicate components of living habitat for rockfish.

Howe sound dive team Vancouver Aquarium

Young quillback rockfish nestling in deteriorated tissue of a cloud sponge.  A loss of opacity and change in colour precedes collapse of dead skeletal tissue of cloud sponges killed by warming seawater.

Early signs of tissue stress and damage are not easily discerned by the average diver. Divers counting rockfish in the Aquarium’s current Annual Rockfish Survey may find rockfish around cloud sponges, especially juvenile quillback rockfish which take refuge in the cover of cloud sponges. When a rockfish settles on dying tissues of cloud sponge, fragments tend to break off. The fish probably does not cause the damage. Cloud sponges cannot tolerate temperatures of 10 degrees Celsius and higher. This year citizen scientists participating in the rockfish survey can provide added scientific information by obtaining photographs of the condition of cloud sponges that are being used for hiding places by rockfish.

The U.S. government agency that tracks ocean El Niño events, NOAA/NMFS, has modified its criteria for ranking El Niño status. These new criteria indicated in August that 2015 was not yet officially into an El Niño event even though such status became official for five months as of September (a five month period is required as a minimum). The previous criteria, which are still depicted on-line, show the 2015 El Niño well underway (10 months as of September). Howe Sound cloud sponges are clearly demonstrating that they consider that El Niño conditions were occurring as of August, so the question is whether the new or previous criteria are more relevant.

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