Last year, we brought a CTD with us to Catalina Island for our culture work. It was the first year (that I'm aware of) that a CTD has been used for culture work at Catalina. In the past, a CTD (which stands for conductivity, temperature, depth) wasn't necessary because divers collected the shallow dwelling spinose forams within the mixed layer and at shallow depths (usually less than 6m). I study forams that live MUCH deeper in the water column, far too deep for divers to collect the specimens by hand (25-55+ m). While we still have divers in the water collecting the spinose specimens (we have many collaborators interested in the spinose forams) we are also doing plankton tows to collect deeper dwelling species. The CTD has been very useful in helping us determine the depth at which we should target our tows. Studies have suggested that the depth habitat of N. dutertrei, the species we are culturing, is associated with the depth of the chlorophyll maximum. This year, Ann (Co-PI-Dr. Ann Russell) had a fluormeter added to the CTD so that we could also locate the chlorophyll maximum and target our plankton tow depths. We typically bring the CTD out with us, do a CTD cast, put out two nets (one shallow and one deeper). We then download the data back in the lab and we can compare the abundances of forams collected with the depth of the Chl-Max AND (importantly) use that data to target the depth of our next tow. We typically don't download the data on board because divers are usually on the boat at the same time - which makes for a REALLY wet boat - not a great place for a computer. But, we've found that often the water masses change so quickly here that by the time we go out on another collection, the chlorophyll max may be a bit deeper (or shallower).
What have we learned so far about the deep dwellers and their abundances? Well... sometimes we don't find ANY N. dutertrei in the Chl-max. Abundances are quite low this year and juvenile specimens (those that are ideal for culture) peaked just after the full moon. Two weeks after the full moon, abundances were still high, but the specimens are HUGE. So big, in fact, that they will do nothing in culture except die (too big add chambers). We have a hunch that the next round of very small specimens will peak after the next full moon. O. universa abundances typically track the lunar cycle and this year, that has been the case. Perhaps this will hold true for N. dutertrei. We have found that 'typically' N. dutertrei abundances are correlated with the Chl-Max (though those specimen are fully calcified and at the end of their life cycle) and abundances of juveniles (depth of which varies) may be correlated with a periodic reproductive cycle that may be correlated with the lunar cycle. Sure is a lot of correlated correlations!
Coming up in the next post... new chambers vs. pre-gametogenesis... pictures and more!