Beyond the hustle and bustle of the Santa Cruz Boardwalk and the sound of waves crashing against the sand we head offshore and down into the ocean. Beyond the last twinkle of sunlight we find amazing ‘coral’ organisms in the deep-sea ocean. Like their surface ocean, tropical cousins, these macrofauna provide habitat and ecosystem services including for commercially important groundfish (e.g., sea bass, cod). These colonial organisms build their skeletons out of calcium carbonate and-or wind organic proteins into a tough, horny home.
In many places only since WWII and most places only since the late 1800s do we have direct measurements of environmental and oceanographic variability. To extend these records and develop a fuller understanding of natural climate variability we look to sedimentary and biological archives; like deep-sea corals. Locked within the skeleton of deep-sea corals are records of past environmental and climate variability. Because of their longevity and that they live in places where we have not frequently ventured, one of the most exciting prospects is to use the chemical and isotopic signatures in deep-sea corals to reconstruct what has happened over their life-span.From deep-sea carbonate coral skeletons we can determine past changes in (interior) water temperature, nutrient concentrations, and pH. Organic and proteinaceous skeletons contain a detailed record of past changes in surface water sources of carbon (ie. who made up the phytoplankton assemblage) and nutrient cycling of unsurpassed fidelity.
From the organic skeletons of deep-sea corals recovered from near Hawai’I in the North Pacific Subtropical Gyre we have documented concomitant changes over the last 1000 years in the source of nitrogen being used by phytoplankton and changes in community structure (which phytoplankton were growing). Not surprisingly the phytoplankton community and sources of nitrogen change with large scale climate forcing.Most recently, since the end of Little Ice Age (~1850) and the beginning of the industrial era, we have entered a period of increased stability of the water column including surface warming and an expansion of the gyre. This has resulted in a phytoplankton community that is unique in at least 1000 years!
We have barely explored the world’s oceans: only about 20% have been mapped in detail. To a large extent, we know more about the surface of the Moon than we do about Earth’s oceans. The mesopelagic, otherwise known as the ocean’s twilight zone, extends from 200 to 1000m below the surface of the ocean. Linking all of the world’s oceans, it is the largest continuous ecosystem and biome on Earth. The mesopelagic is home to familiar looking creatures (e.g., seastars, urchins) as well as unique and, to those of us on land, alien looking life such as mid-water gelatinous creatures and deep-sea corals – both hard and soft. Many of the deep-sea corals and related biota have lifespans that exceed most terrestrial counterparts: many genera have colonial lifespans of a hundred or more years, with colonies of some genera continuously being added to for thousands of years. Although out of sight, through our actions and choices humans can impact these delicate and important ecosystems.