Evolution and Adaptation

Decisions, Decisions

Figure 1. The gloriousness that is Oreos. Look at that! Apple pie flavored Oreos. Truly we live in a magical time.
Figure 1. The gloriousness that is Oreos. Look at that! Apple pie flavored Oreos. Truly we live in a magical time.

Gabriel Ng

“There’s no such thing as a free lunch.” “You can’t have your cake and eat it too.” Tradeoffs: it’s an intuitive concept that we grasp and grapple with in our everyday lives. Any decision we make has some benefits but usually incurs some costs also. Do I buy this box of Oreos or use that cash to purchase some broccoli? (The answer is always Oreos). Do I go barhopping with friends or spend my time studying? The balance of costs and benefits are parameters we factor in every time we make a decision. And for the most part, these decisions are relatively easy. Rarely do we find ourselves paralyzed with indecision as we traverse about our daily routine. I’m not drooling off into space during breakfast as I decide whether I should use 3 tablespoons of coffee to ration my supply or 5 tablespoons to ensure I get my hit of caffeine.

Figure 2. This is my study snail, Tegula funebralis. It may not look like much, but it has a pretty intense fear response when it smells predator in the water. Here it is doing what it knows best, leaving the water when it is afraid.

However, there are times when the tradeoffs within a decision are tremendously complicated. Cost-benefit analyses only work when they are directly comparable, i.e. in the same units. Yet, most tradeoffs involve outcomes with differing values. How does one exactly evaluate the time spent with one’s offspring (I assume that’s a good thing. I don’t know. Kids are icky) versus the effort spent working overtime? You can’t compare apples and oranges because well… they are apples and oranges. Now, an economist might argue that we can distill decisions down to monetary value. A hedonist focuses on happiness units. Though we can try to reduce our decision outcomes to some common currency, we also lack perfect information. What are the opportunities we miss out on every time we make a choice, aka opportunity costs? There may not be a direct cost to milling around in bed watching Netflix during the weekend, but that time could have been spent finding the cure for cancer (or something equally as productive).                      

fear response
Figure 3. The fear response in Tegula funebralis is effective in escaping predation but it incurs the cost of unable to feed while out of water. So what’s the tradeoff if it doesn’t leave the water and instead continue to forage when a predator is around? I will leave the photo of a crab plus Tegula funebralis shell fragments as the answer (it was a massacre).

But why I am talking about human decision making in a marine science blog? I don’t study human behavior. I study something much more exciting: snails along the rocky intertidal. While these animals do not face the same tradeoffs that we do, they have their own suite of complicated decisions they must make everyday. How should it allocate its time feeding versus avoiding predatory crabs? Is it worth competing with another individual over a seaweed patch or better to find a lower quality patch with no competition? Like us, these snails face the same complications when considering tradeoffs except the stakes are literally life and death. What makes this system particularly interesting to study is that the optimal decision among the various tradeoffs has already been solved through millennia of evolution. And I want to know why that particular decision is the best given the current environment. Sure, my research may never allow me to figure out the optimal ratio of Oreos to broccoli I should buy (I have a hunch it’s all Oreos and no broccoli), but knowing why snails behave as they do can provide further insight on the inner workings of our intertidal coastline.


Water weeds. Love ‘em and leave ‘em be.

Water weeds. Love ‘em and leave ‘em be.

By Alisha M. Saley

Growing up I was no different than the rest when it came to water “weeds”. I was terrified to feel the slime and whip-like stalks wrap around my legs as I waded into streams and lakes. The horrifying mixture of slippery rocks (diatoms), feather-like strands of filamentous algae on my legs, and squishing sediments between my toes sent strains of panic up my spine. As kids we perpetually persevere; my focus at the time to remain as close to the water surface as possible so as not to contact the dark abyss of the stream bottom (and the horrific photosynthesizers) again.

As it turns out, my disdain for the proliferation of these photosynthesizers was severely misplaced. In fact, most play a crucial role in supporting whole stream ecosystems. Other than providing a food source and refuge for small-bodied animals, they have sizable control over the hydrological flow of the system, specifically in smaller streams. Moreover, through uptake of excess nutrients (fertilizers from agriculture) into their tissue and the deceleration of flow (increasing sediment deposition) they serve as a biological filter. This ensures that the water that confluences with larger waterbodies downstream is less turbid (clearer), more oxygenated, and lower in superfluous nutrient concentrations.

With all biological beings, there is a threshold for functional success. Unfortunately, the increasing pressure we are putting on these systems to “clean up our extras” has surpassed their ability to remove our footprint. For example, we now have an annual, spring harmful algal bloom and hypoxic (low oxygen) zone that forms at the mouth of the delta of the Mississippi River (Figure 1). This bloom results from the transport and accumulation of excess nutrients (nitrogen and phosphorus) that were previously applied to farm fields upstream. This region of eutrophication (high productivity) stimulates toxin-producing algae to rapidly take up these nutrient resources, releasing toxins that are harmful to other animals (including humans). As nutrients deplete, the algae die and sink deeper in the water column. Microbes break down the dead tissue and through microbial respiration deplete the area of oxygen, making it unsafe for other species that require oxygen from the water to breathe. Those that are mobile flee the scene to areas of higher oxygen concentrations; however, many slow or sessile (non-moving) organisms are left to die.

figure 2

Although we have a general understanding of the aquatic cycling of nutrients, less understood is the relative roles that specific photosynthesizers have in uptake. For example, we know that for any one set of environmental conditions (light, temperature, flow, etc.), some photosynthesizers will be better competitors (i.e. will uptake more nutrients). However, natural conditions are ever-changing and as such, scientists now seek to understand what happens to shift in competition within communities (Figure 2). Therefore, along with mapping physical flows of nutrients, scientists are trying to map localized nutrient cycling in and out of organic material (photosynthesizers). This information can potentially aid management entities in creating natural, biological “nutrient barriers” (plant buffering zones) that sequester nutrients in pulse regimes, therefore reducing the impact agricultural entities have on neighboring waterbodies.

As an aquatic scientist I again find myself wading into the muck and grit and slime of streams, however my fear no longer stems from wispy plants and fuzzy algae. Instead I fear for ecosystems downstream of “the weeds”, as we already see how life is destroyed without their filtering capacity.