Friday, August 1, 2014

Post-field work, Pre-data analysis report

So now that I have left Kent Island, data collection has (obviously) stopped, though I have left all of my plates in the water for a later data collection expedition in September. Where does this leave my project?

The main part of my project was to examine the effect of current on species diversity in settlement communities by looking at racks of plates suspended all around the island. Below is a map showing placement sites (now I realize that all this time I have been referring to places on Kent Island without actually providing a reference map!)

High Flow treatments were in two locations as indicated by green placemarks: the extreme southern end around the giant tide pool exposed to high surf conditions and the extreme north between Kent and Hay Islands where tidal current rips through. One low flow treatment is at West Beach as indicated by yellow placemarks. Red placemarks indicate missing or lost plates as of 07/26/14.

After six or seven weeks (depending on date of original placement), no growth of any target organisms was seen on the plates. A biofilm of alage, diatoms, and ostensibly bacteria was present on all plates, and on several snail or nudibranch eggs were observed.

Pictured above and below are Plate 3 from the Narrows High Flow treatment rack at week 1 and week 7 (above and below respectively). Note extensive algal growth and snail eggs below but no target settlement organism growth. These plates are representative of what I am seeing after 7 weeks, but obviously other trends exist. 

So what does this mean? Why aren't organisms growing? So far I am hypothesizing that water temperatures around Kent Island are too low to trigger spawning and settlement of planktonic young. Temperatures averaged 8 degrees celsius for most of June and only began to approach 11 degrees in July, generated by the cold Nova Scotia current from the north-east. This is not cold enough to disallow growth and spawning overall, however, since I counted at least 28 settlement organism species in my quadrat plots. However, the warmest water temperatures are not reached until late August/early September, when I predict most organisms will spawn (to be confirmed with background research). Furthermore, most of the invasive tunicates I am looking for are actually spawning intolerant below 14 degrees C, indicating that perhaps Kent Island will escape the hordes of invasive solitary and colonial tunicates that are taking over in warmer waters just a few miles west in Eastport and further south as well as the unusually warm waters in the Northumberland Strait by Prince Edward Island. It is very probable that this 14 degrees C threshold will be reached at Kent Island, but the time window would be quite short, limiting the amount of larval recruitment that could actually occur. I would predict, however, that as ocean temperatures rise in the coming decades due to climate change that we will see earlier and earlier spawning-tolerant temperatures around Kent Island, perhaps triggering a sudden invasion around the island. I would hope that some kind of monitoring program could be set up around Kent Island to track this progress.

Preliminary temperature graph at 1m depth at High Flow treatment south pool, Kent Island, for the dates 06/10/14-07/23/14.  Gap in data from 07/01/14-07/08/14 was due to logger removal during a hurricane to prevent logger lost. Title is incorrect in dates, note time shown extends from June 10 to July 22.   

I hope to update this blog with final results as they come in September and October, but overall it has been an incredibly difficult but rewarding time here on Kent Island. My project in its current manifestation is perhaps not too well suited for the Kent Island environment (that is, there exists a major physical barrier preventing my experiment from preceding), but I am quite interested in the advancement of invasive organisms onto Kent Island and I hope students examine this issue in the future.

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