Design of Ocean Waste Recyclers

Design of Ocean Waste Recyclers

I grew up within easy walking distance of Burrard Inlet in Vancouver, one of the world’s busiest harbors. The water of that port is filled with thousands of sea creatures, such as gulls, fish, crabs, clams, barnacles, starfish, sea urchins, and sea cucumbers. I recall spending one afternoon as a young boy figuring out the amount of waste deposited daily into Burrard Inlet by all these animals. The number I calculated was so high that I concluded some life-forms must exist in the port to eat most of the waste. At that time, marine biologists had little knowledge of what such life-forms might be.

Today, researchers have identified such creatures, unicellular organisms called chemotactic marine bacteria. They are known as “chemotactic” because they direct their movements toward or away from certain chemicals in the environment. These bacteria are the primary organic waste-recycling organisms in the oceans. Such bacteria not only eat and reprocess fish and bird droppings but also consume the far more abundant waste produced by phytoplankton. (Phytoplankton are responsible for about 70 percent of Earth’s photosynthetic activity.)

A long-standing question, answered only recently, asked how chemotactic marine bacteria are able to so efficiently and effectively recycle most of the waste generated by sea animals and phytoplankton into the minerals that phytoplankton need for optimal growth. One problem is that the bacteria must be able to position themselves—without expending too much energy and, hence, dying—to exploit the food sources.

Two oceanographers, Roman Stocker and John Taylor, report on a computer model of ocean turbulence they performed that solved the mystery. Stocker reviewed the status of experiments exploring microturbulence in the oceans, the variety of nutrients on microscales in the oceans, and the ecosystem of chemotactic marine bacteria.1 Stocker and Taylor also described how their numerical simulations revealed (for the first time) designs and design tradeoffs of chemotactic foraging in turbulent ocean waters.2

Stocker and Taylor reference measurements that establish that the smallest scale at which turbulent velocity fluctuations occur lies between 1–10 millimeters. Motile bacteria are able to exploit nutrient gradients in the oceans if their motility range (distance they can cover over the lifetime of a nutrient patch) is greater than that of a tiny range called the Batchelor scale. In other words, microturbulence stirs organic wastes in the oceans into concentrated filaments. Thus, if chemotactic marine bacteria can make their way from the relatively waste-free voids to the filaments, they will find rich, easy-to-harvest food sources.

Stocker and Taylor observed that the average milliliter of seawater contains about a million chemotactic bacteria. Some of these bacteria are motile. Others are nonmotile.

The nonmotile chemotactic marine bacteria lack the hardware and the energy support systems necessary for transportation in ocean water. Consequently, they expend less energy than their motile cousins. They also differ from their motile cousins in that their metabolic rates are very low. Lacking mobility structures and designed to function at very low metabolic levels, nonmotile chemotactic marine bacteria have energy needs that are so low they can survive on the tiny amounts of organic wastes that exist in the voids.

The motile chemotactic marine bacteria, by contrast, are endowed with mobility structures to ensure that the bacteria can move from filament to filament at speeds that produce the greatest return on energy investment. That is, the motile structures and the manner in which the bacteria employ the structures are such that the bacteria expend the minimum possible amounts of energy to travel to nutrient-rich filaments. They are designed to travel at speeds not so high as to waste energy getting to the food-rich sites and not so low that they exhaust their life-essential energy stores before getting to the sites.

Stocker and Taylor’s research reveals multiple exquisite designs. First, there are two levels of microturbulence design in the world’s oceans. Both the range of spatial scales for the microturbulence and the range of microturbulence magnitudes are optimized to maximize chemotactic bacterial foraging. Additionally, the structures, metabolic rates, and behaviors exhibited in the nonmotile and motile chemotactic marine bacteria display elegant arrangement. Such multifaceted exquisite designs signify the work of the superintelligent, supernatural Creator God of the Bible.

  1. Roman Stocker, “Marine Microbes See a Sea of Gradients,” Science 338 (November 2, 2012): 628–33.
  2. John R. Taylor and Roman Stocker, “Trade-Offs of Chemotactic Foraging in Turbulent Water,” Science 338 (November 2, 2012): 675–79.