The storms of the past week cleared most of the pack ice out of Arthur Harbor, although the land fast ice that we’ve been sampling from has survived. In anticipation of the start of the boating season there was a flurry of activity yesterday as station personnel cleared off the boat ramp and got the zodiacs ready. Unfortunately Jamie and I didn’t think to start the time lapse below until yesterday afternoon after most of the three-ring circus had died down, but you still get a sense of the activity.
There are two science groups waiting to start boating operations; our group and a group of penguin researchers (aka “the birders”). Both groups are part of the Palmer LTER. While we will spend the summer investigating water column processes however, the birders will spend their summer visiting the various penguin rookeries and maintaining a remarkable long term dataset of penguin population.
Taken from Ducklow et al. 2013. The birders do far more than just count penguins; they analyze diet, physiology, breeding success, and a host of other factors. The number of penguins alone however, tells an interesting story. Since the mid-1970’s the number of adélie penguins along the West Antarctic Peninsula (or at least at those rookeries that we can access and monitor) has declined sharply. There are good indications that this is related to the general decline of sea ice in the area. A high ice year like we are having right now might be good for the adélie’s but the situation is complex. The ice has been good but the weather is also warm and wet. Warm, wet conditions are extremely hard on adélie penguin chicks and can lead to large (at times total) breeding failures.
The birders were supposed to get their final zodiac training today, but although the harbor is clear of ice the winds are back up (gusting around 30 kts at the moment) so everything is getting shifted back. In the meantime we will have a late night sampling another time point from the experiment that we started on Tuesday. As I described in the previous post, for this experiment we are making use of the highly unusual ice conditions to study what happens to the microbial community when the ice is suddenly removed (as has happened to much of Arthur Harbor and the surrounding area in the last week). Although we won’t know the results of most of our analyses for several months, we can make some interesting qualitative observations as the experiment progresses.
One of the interesting observations so far was the initial condition of the microbial community. During a down moment yesterday I took a look at water from just 24 hours into our experiment to see what was growing (so this isn’t exactly the initial condition, but a close approximation of it). What we found really surprised me. Here are a couple of images that illustrate the phytoplankton community in our experiment:
By far the most abundant phytoplankton growing under the ice in Arthur Harbor right now. The size (about 10 microns) and teardrop shape suggest that it is a cryptophyte. This is interesting because many cryptophtes are mixotrophic; in addition to undergoing photosynthesis they can consume bacteria as a source of carbon.
A small pennate diatom. This is the only one that I could find but, and this is purely speculative, it looks like it might be dividing. Magnification is the same as the previous image, so I would guess that this cell is 10-20 microns in length.
The traditional wisdom would suggest that the spring phytoplankton bloom should start with diatoms. Following the initial diatom bloom there are successive, mixed blooms of haptophytes, cryptophytes, dinoflagellates, and other groups of phytoplankton. Observations from this time of year are very sparse however, so it is difficult to know if we are seeing something that is unique or the normal phytoplankton assemblage for this time of year. The composition of the phytoplankton assemblage is not merely academic; it dictates how carbon will flow through the food web in a given season. Large diatoms for example, are easily feed upon by krill, resulting in high krill biomass and more and more healthy top predators (e.g. penguins, seals, and whales). Smaller phytoplankton (like cryptophytes) produce a more complex food web that might ultimately channel less carbon to the top trophic levels. We will have to wait and see how the situation plays out this year…
