Scientific diving

Scientific diving is the use of underwater diving techniques by scientists to perform work underwater in the direct pursuit of scientific knowledge. The legal definition of scientific diving varies by jurisdiction. Scientific divers are normally qualified scientists first and divers second, who use diving equipment and techniques as their way to get to the location of their fieldwork. The direct observation and manipulation of marine habitats afforded to scuba-equipped scientists have transformed the marine sciences generally, and marine biology and marine chemistry in particular. Underwater archeology and geology are other examples of sciences pursued underwater. Some scientific diving is carried out by universities in support of undergraduate or postgraduate research programs, and government bodies such as the United States Environmental Protection Agency and the UK Environment Agency carry out scientific diving to recover samples of water, marine organisms and sea, lake or riverbed material to examine for signs of pollution.
Equipment used varies widely in this field, and is generally selected based on cost, effectiveness, availability and risk factors. Open-circuit scuba is most often used as it is widely available and cost-effective, and is the entry-level training mode in most places, but since the late 1990s the use of rebreather equipment has opened up previously inaccessible regions and allowed more reliable observations of animal behaviour.
Scientific diving in the course of employment may be regulated by occupational safety legislation, or may be exempted as self-regulated by a recognised body. The safety record has generally been good. Collection of scientific data by volunteers outside of employment is generally considered to legally be recreational diving.
Training standards vary throughout the world, and are generally higher than for entry level recreational diving, and in some cases identical to commercial diver training. There are a few international agreements that facilitate scientists from different places working together on projects of common interest, by recognising mutually acceptable minimum levels of competence.

Scope of work

Scientific diving is any diving undertaken in the support of science, so activities are widely varied and may include visual counts and measurements of organisms in situ, collection of samples, surveys, photography, videography, video mosaicing, benthic coring, coral coring, placement, maintenance and retrieval of scientific equipment.
The importance of diving to the scientific community is not well recorded. A bibliographic analysis of papers published between 1995 and 2006 that have been supported by scientific diving shows that diving supports scientific research through efficient and targeted sampling. Activities include collection of organisms and biological samples, observing animal behaviour, quantitative surveys, in situ measurements, impact studies, ecological analyses, evaluation of techniques, mapping underwater areas, profiling geology, and deploying and retrieving underwater equipment.
A comparison of database searches against a selection of publications known to have used scientific diving in the same period, shows that a small minority of papers were discovered, suggesting that the importance of scientific diving as a valid and cost-effective underwater research tool is greatly underrepresented in the literature.
Some underwater work in support of science is out of scope of the relevant regulations, exemptions, or codes of practice, and is not legally classed as scientific diving. This work is required to be done by divers trained, registered, and operating following commercial diving health and safety practices.

Contribution of scientific diving to research

Underwater diving interventions, particularly on scuba, provide the capacity for scientists to make direct observations on site and in real time, which allow for ground-truthing of larger scale observations and occasional serendipitous observations outside the planned experiment. Human dexterity remains less expensive and more adaptable to unexpected complexities in experimental setup than remotely operated and robotic alternatives in the shallower depth ranges. Scuba has also provided insights which would be unlikely to occur without direct observation, where hypotheses produced by deductive reasoning have not predicted interactive and behavioural characteristics of marine organisms, and these would not be likely to be detected from remote sensing or video or other methods which do not provide the full context and detail available to the diver. Scuba allows the scientist to set up the experiment and be present to observe unforeseen alternatives to the hypothesis.
The field of global change biology includes investigation of evidence relating to global warming and ocean acidification. Many of the measurable changes in global climate occur in the sea. Coral bleaching is an example of an indicator of change, and scuba diving has provided a large amount of low-impact observational data contributing significantly to the large body of knowledge on the subject over several decades.
The field of ocean acidification and the impact of anthropogenic carbon dioxide emission has seen similar growth and most of the cited articles in this field have relied to a significant extent on data collected during scuba diving operations.
The field of paleoclimate reconstruction has a major influence on the understanding of evolution and the ecological and biogeographic past, as climate is the most powerful driver of evolution. Coring corals on a reef in the least harmful and most focused manner is currently most practicable using scuba technology. This mining of the past makes it possible to attempt to predict future climate.
Advances in training and accessibility to trimix diving and closed circuit rebreather systems has enabled scientific divers to reach highly diverse deeper mesophotic reefs which may be the corals last refuge from the warming of surface waters.
The current knowledge of the functioning of the ecologically and economically important hard-bottom communities in the shallow water coastal zones is both limited and particularly difficult to study due to poor accessibility for surface operated instrumentation as a result of topographic and structural complexity which inhibit remote sampling of organisms in the benthic boundary layer. In situ assessments by scientific divers remain the most flexible tool for exploring this habitat and allow precise and optimised location of instruments.
The capacity to dive under polar ice provides an opportunity to advance science in a restricted environment at relatively low cost. A small number of holes in the ice can provide access over a large area and high levels of experimental replication. Divers are a flexible and reliable method for deploying, maintaining and retrieving equipment from under‐ice environments, and are relatively cost efficient for researching remote locations that, would otherwise require the use of more expensive research vessels.
The global threat to marine ecosystems due to over‐exploitation, habitat loss, pollution and climate change is exacerbated by introduction of alien species, which is considered to be one of the leading causes of extinctions and biodiversity loss. Scientific divers are the most competent to detect the presence of potentially invasive species and in some cases can provide a quick response. Monitoring the effectiveness of response also requires diver intervention.
Underwater archaeology has developed considerably over the past century, and diving allows a site to be excavated with minimal disturbance of the site or damage to artifacts.
It was observed that personal intervention by the scientist allowed more accurately targeted observations and less incidental damage compared to blind sampling from the surface, and that the observation of the subject by the scientist can provide valuable and often unexpected data. There are also phenomena and organisms that are difficult or impossible to observe except by being there, and places that are difficult to access other than by going there in person. It is difficult to determine the full scope of underwater science in the past, as not all work or methodologies have been published.

Diving activities in support of research

Sampling: Diving is highly selective and useful for sampling delicate materials or organisms, and for collecting from specific locations or associations, it can be more efficient than sampling methods relying on chance, and can be cost-effective compared with the use of research vessels. In some cases there is no other way to gain access to the specimen, or the specimen must be actively searched for and visually identified, before extracting it from a complex environment without damage. Diving can produce higher quality samples with less collateral damage. Specimen collection of animals is more prevalent, but algal specimen and sediment core collection by diver can produce better quality samples in many cases.
Survey and quantitative observation: Surveys and quantitative assessments may comprise quantitative descriptions of biotic assemblages, distribution or abundance of a species or group or other feature, or relate the topography of the seafloor to the distribution of a species or group. There are examples where ROVs and video surveys have been used for these purposes, and the alternatives each have their advantages.
Animal behaviour: Behaviour tends to be studied by direct observation, video or time lapse photography. In many cases the equipment is deployed and recovered by divers, allowing judgement to be exercised in the setting up process. There is debate on the extent of the influence of divers and monitoring equipment on animal behaviour, and the behaviour may be influenced by the type of equipment used by divers using open or closed circuit equipment, as the noise and presence of bubbles is known to affect fish behaviour. Reproductive behaviour, territoriality, predator-prey interaction and movement have been studied.
In situ measurement: In situ measurements by divers eliminates the need to remove the target from the water. This has the potential for more accurate data with less disturbance of the environment, but is not always practicable.
Impact and/or pollution studies: Diver observation can be quick and effective at identifying the scope and extent of disturbances, and samples and measurements can be taken where effects are observed, but risk to the diver must be considered, and in some instances the presence of the diver may constitute a significant impact, and studies have been done to assess the environmental impact of recreational divers on fragile tropical reef or cave environments.
Ecological studies: The study of distribution, abundance and interactions between organisms and with the environment is a combination of activities already mentioned. The presence of a diver allows serendipitous observations to be followed up in real time, which is particularly valuable when the observation is a rare occurrence.
New species or first reports: Discovery of new species or recording range extensions relies on first noticing the presence of the organism, then recognising that it is unexpected, and either making a collection or recording sufficient evidence of presence and identity. There is no adequate substitute for the presence of a sufficiently knowledgeable diver with the right equipment. In many cases unexpected organisms have been observed, reported, and never found again.
Technique evaluation: The evaluation of new techniques and the comparison between existing techniques of investigation and data gathering is a common procedure, not only for techniques used by divers, but also of the operation of remotely controlled equipment and surface deployed equipment. Observation of the operational performance can identify flaws and potential for improved design of equipment and operation and help validate the method.
Mapping and/or ground-truthing: Direct survey by divers may be necessary or preferable, depending on what is to be mapped. Distribution maps require the targeted subjects to be recognised reliably and accurately, and in some cases this can only be done by an expert observer. Remote mapping technologies require validation of accuracy, precision and reliability. Various methods may be used, including using divers to physically validate points on the map.
Geology or geological profiling: This is uncommon, but can include straightforward observations of the general submerged geology and distribution of sedimentary facies, and the collection of samples.
Deployment and/or retrieval: Diver deployment and retrieval of apparatus allows careful and precise placement, which may be necessary to gather the desired data, or to avoid adverse impact on the environment. Recovery may also require careful work, to avoid damage to environment or equipment.
Hydrothermal studies: Divers have been used to locate, identify and sample from isolated or specific vents.
Tag/recapture: Divers have been used to tag and recapture animals. This may be relatively easy with slow-moving benthic species, but can be quite difficult with others. In situ tagging and release exposes the subject to less risk of barotrauma.
Biotechnology and/or pharmacology: Targeted collecting of species for pharmacological investigation should improve the probability of new discoveries, but this is equally valid for other methods of directed collection.
Geochemistry and/or biogeochemistry: Divers have been used to sample distribution of surface sediments, and to take core-drilled samples of coral reefs.