Types of impact Underwater macro photographer resting on the bottom while composing a photo Diver kicking up the sand with wash from the fins Diver kneeling on the sand in the Comores, note the dangling instrument combo Diver feeding fish at Cod Hole Research on the effects of divers on tropical coral reefs has shown reduced coral cover on heavily dived sites and a change in coral structure, with more resilient corals becoming dominant and a loss of species diversity over time. These reefs may be less resilient to other stressors like disease outbreaks and severe weather damage.  In some frequently dived tropical coral reef sites recreational divers have caused negative ecological impacts by inadvertent impacts with live corals causing physical damage at a rate faster than compensated for by natural recovery. The long term result is reef degradation. One of the common challenges for local policy and management is maximising tourism benefits while also reducing environmental degradation to long-term sustainable levels.  The impacts of photographer behaviour and photographic flashes on a small sample of benthic fish species was investigated. The study showed negligible effects beyond those caused by human presence alone. Flash photography caused no discernible ocular changes in seahorses and feeding success was not affected. Physical handling of animals produced strong stress responses.  The impact of recreational scuba diving on recreational dive values and the cultural heritage of shipwrecks has been found to comprise four basic types: The removal of artifacts and associated disturbance to wreck sites, Direct contact with wrecks and the benthic biota living on them by divers and their equipment, Exhaled air bubbles trapped inside the wreckage, Impact damage by anchors of dive boats, considered by some researchers to be the most damaging form of impact associated with recreational wreck diving. Shot line weights can also damage relatively fragile wreckage by impact and snagging, but usually to a lesser extent as the shot is generally lighter than an anchor or and there is less lateral load on it. This type of damage can be avoided completely by installing permanent moorings at frequently dived wrecks. Reasons for impact  Repetitive contact by divers and their equipment on the benthos is the general mechanism of reef degradation by recreational divers. Factors correlating with frequency of reef contact were found to be: Interval since the previous dive Experience in terms of number of dives to date Location of certification training Awareness of marine park zoning Use of photographic equipment - photographers are more likely to contact the reef while their attention is focused on taking a photo. Depth of the dive – divers were observed to make fewer contacts at greater depth. The reasons are not clear, but may be related to less water movement or less buoyancy variation with depth. Large groups of divers gathering at the beginning of a dive before they establish neutral buoyancy A considerably higher rate of impacts has been observed during the initial phase of dives and has been attributed to divers taking some time to get their bouyancy correct and to get themselves orientated, particularly when entry points are directly over shallow coral formations, or the divers are unfamiliar with the environment.  Observations that experience does not predict frequency of impacts is not necessarily incompatible with findings that practical training reduces frequency of impacts, as experience is not always an indicator of competence. There appears to be little correlation between site topography and coral damage, but damage is related to coral morphology and structural strength. Most damage is to branching species which are inherently weaker against bending loads.  Several studies have found the main reason for contact by inexperienced divers to be poor buoyancy control. Studies on recreational divers on tropical coral reefs have shown that the rate of contact between diver and environment varies significantly between divers who are able to maintain neutral buoyancy and those who are deficient in the skill, with divers who do not maintain neutral buoyancy contacting the reef more often. Briefing divers on the effects of contact with the reef reduced contact in divers with good buoyancy skills, but not in divers who lacked those skills. The problem appears to be one of competence. Without the necessary competence, divers are unable to modify their behaviour appropriately, and cannot produce the skills merely by being made aware of their necessity. The solution to reducing reef contact is in requiring the diver to have the skill before allowing them to dive in the environment where it is needed. Strategies for reducing diver impact Diver with dangling instrument console, which could impact the bottom or even get snagged on a reef Correct weighting is a prerequisite for good buoyancy control. Good buoyancy control is necessary (but not sufficient) for sustained level trim. Level trim brings fins higher above the benthos on most reefs with consequent lower frequency of direct contact and of disturbed sediments. Reduction and clipping off of dangling equipment reduces the risk of low-hanging items contacting reef when in close proximity. Awareness of proximity to the surroundings allows avoidance of movements which will result in reef contact, particularly high impact contact. Appropriate finning technique should reduce risk of reef impact, and can be selected to suit lateral or vertical proximity. Understanding the ecological effects of reef contact and knowledge of the vulnerabilities of local species allows avoidance of particularly vulnerable organisms, and is likely to motivate ecologically responsible divers to apply more effort to avoiding contacts. Adjusting proximity to suit sea conditions – clearance between diver and benthos can be adjusted to allow acceptable risk of contact for variations in surge and current. Low impact diving training Diver trimmed head up produces downwash vortices while finning which lift bottom sediment. Scuba training should be done where it has no direct impact on the environment if possible Diamond Reef "rollercoaster" course layout for low impact skills training and evaluation Wreck diver keeping clear of the wreckage while swimming through an fairly confined space Sidemount diver trimmed well to avoid contact with the bottom on a temperate granite reef in False Bay near Cape Town Low impact diving training has been shown to be effective in reducing diver contact. Strategies for sustainable use management  Several methodologies have been developed with the intention of minimising the environmental impact of divers on coral reefs Carrying capacity approach, where the number of divers is restricted. This also limits tourism income from the region. Sustainable diver carrying capacity is influenced by factors which vary between sites. These include coral morphology, presence of vulnerable species, environmental awareness and competence of the divers, presence of other stressors, size of the dive site, reef topography, and sea conditions. Continuous adjustment may be necessary to account for changes, unknowns and inaccurate models. Limits of acceptable change. This model uses quantitative limits on change defined in specific management objectives for a site using an established baseline. It does not handle natural variation well if this is unknown, and cannot distinguish between causes of change, some of which may be unrelated to diving. In some cases an undisturbed baseline may not be available. Percentile approach: This method considers a need for multiple reference sites and establishes trigger values quickly by comparing the extent of coral damage between dived sites and similar non-dived control sites. The trigger for management action is if the median abundance of damage to coral equals or exceeds the 80th percentile of damage at the reference sites. Limitations to this system include sensitivity to initial conditions - it does not work well if the reference sites are already significantly degraded, and permanent moorings tend to concentrate damage to the region near the mooring, it may pick up false positives from damage from non-diver causes, and it is sensitive to conditions at the control sites. Restricting recreational divers to delimited locations, which usually concentrates divers and damage along diving trails. This creates paths of degraded reef through the more pristine areas, and will cause customer dissatisfaction as the trail degrades further. Regulating the type of diving equipment allowed, generally accessories which are thought to increase reef contacts, such as gloves and cameras. These restrictions are understandably unpopular with photographers, and may be applied to both divers who manage to avoid contact and those who do not. Cost and complexity of photographic equipment does not correlate well with diving competence. Changing the methods by which the industry provides services: Closer supervision and intervention by dive guides can reduce diver contact rates where the divers are sufficiently skilled to modify their behaviour during the dive. It does not address basic incompetence, which is common. A pre-dive briefing on responsible behaviour, regulations and environmental values can reduce the rate of diver impacts where the divers are sufficiently competent to avoid contact. Experience was not found to be a strong indicator of competence, but inexperience and lack of regular or frequent practice are generally good indicators of poor buoyancy and trim skills. More effective interventions occur when the ratio of divers to guide is low. Diver carrying capacity  The number of dives over a time interval that results in an acceptable and stable level of degradation depends on a combination of factors that vary between sites. These include the presence of vulnerable organisms, and the stresses to which they are specifically vulnerable, the level of environmental awareness and responsibility of the divers, the diving skills and situational awareness of the divers, prevalent water conditions during dives, including currents and surge which increase difficulty of positional control, other anthropogenic stressors that may be present, and may combine their effects with diver impact, topographical details which affect diver maneuvering and risk of impact, and the size of the site. Continued periodical re-assessment will generally be necessary, even when there are no obvious large changes to external circumstances. These factors may vary considerably even within a specific ecological zone, and may be expected to be very different between for example, a tropical coral reef dominated by branching stony corals on a gradually sloping bottom with persistent moderate wave action and continuous current, in an area far from major industry, and a high profile granite corestone temperate reef with deep gullies and steep ridges, dominated by kelp, ascidians and echinoderms, and with seasonal variations in prevailing wave direction near a large industrial city. The appropriate equipment and relevant skills will also vary, and unfamiliar rental equipment can require some practice before the diver can use it well, particularly for optimising weighting and trim. Divers in training can not be expected to perform at their best while distracted by learning new skills, and this is also a factor to be considered as a potential stressor if there is no separation between training sites and sites for qualified divers.
Types of impact Underwater macro photographer resting on the bottom while composing a photo Research on the effects of divers on tropical coral reefs has shown reduced coral cover on heavily dived sites and a change in coral structure, with more resilient corals becoming dominant and a loss of species diversity over time. These reefs may be less resilient to other stressors like disease outbreaks and severe weather damage. Diver kicking up the sand with wash from the fins In some frequently dived tropical coral reef sites recreational divers have caused negative ecological impacts by inadvertent impacts with live corals causing physical damage at a rate faster than compensated for by natural recovery. The long term result is reef degradation. One of the common challenges for local policy and management is maximising tourism benefits while also reducing environmental degradation to long-term sustainable levels. Diver kneeling on the sand in the Comores, note the dangling instrument combo The impacts of photographer behaviour and photographic flashes on a small sample of benthic fish species was investigated. The study showed negligible effects beyond those caused by human presence alone. Flash photography caused no discernible ocular changes in seahorses and feeding success was not affected. Physical handling of animals produced strong stress responses. Diver feeding fish at Cod Hole The impact of recreational scuba diving on recreational dive values and the cultural heritage of shipwrecks has been found to comprise four basic types: The removal of artifacts and associated disturbance to wreck sites, Direct contact with wrecks and the benthic biota living on them by divers and their equipment, Exhaled air bubbles trapped inside the wreckage, Impact damage by anchors of dive boats, considered by some researchers to be the most damaging form of impact associated with recreational wreck diving. Shot line weights can also damage relatively fragile wreckage by impact and snagging, but usually to a lesser extent as the shot is generally lighter than an anchor or and there is less lateral load on it. This type of damage can be avoided completely by installing permanent moorings at frequently dived wrecks. Reasons for impact Diver with negative buoyancy standing on coral structures on Guam Repetitive contact by divers and their equipment on the benthos is the general mechanism of reef degradation by recreational divers. Factors correlating with frequency of reef contact were found to be: Interval since the previous dive Experience in terms of number of dives to date Location of certification training Awareness of marine park zoning Use of photographic equipment - photographers are more likely to contact the reef while their attention is focused on taking a photo. Depth of the dive – divers were observed to make fewer contacts at greater depth. The reasons are not clear, but may be related to less water movement or less buoyancy variation with depth. Large groups of divers gathering at the beginning of a dive before they establish neutral buoyancy A considerably higher rate of impacts has been observed during the initial phase of dives and has been attributed to divers taking some time to get their bouyancy correct and to get themselves orientated, particularly when entry points are directly over shallow coral formations, or the divers are unfamiliar with the environment. Diver trimmed head up produces downwash vortices while finning which lift bottom sediment. Observations that experience does not predict frequency of impacts is not necessarily incompatible with findings that practical training reduces frequency of impacts, as experience is not always an indicator of competence. There appears to be little correlation between site topography and coral damage, but damage is related to coral morphology and structural strength. Most damage is to branching species which are inherently weaker against bending loads. Diver with dangling instrument console, which could impact the bottom or even get snagged on a reef Several studies have found the main reason for contact by inexperienced divers to be poor buoyancy control. Studies on recreational divers on tropical coral reefs have shown that the rate of contact between diver and environment varies significantly between divers who are able to maintain neutral buoyancy and those who are deficient in the skill, with divers who do not maintain neutral buoyancy contacting the reef more often. Briefing divers on the effects of contact with the reef reduced contact in divers with good buoyancy skills, but not in divers who lacked those skills. The problem appears to be one of competence. Without the necessary competence, divers are unable to modify their behaviour appropriately, and cannot produce the skills merely by being made aware of their necessity. The solution to reducing reef contact is in requiring the diver to have the skill before allowing them to dive in the environment where it is needed. Strategies for reducing diver impact Correct weighting is a prerequisite for good buoyancy control. Good buoyancy control is necessary (but not sufficient) for sustained level trim. Level trim brings fins higher above the benthos on most reefs with consequent lower frequency of direct contact and of disturbed sediments. Reduction and clipping off of dangling equipment reduces the risk of low-hanging items contacting reef when in close proximity. Awareness of proximity to the surroundings allows avoidance of movements which will result in reef contact, particularly high impact contact. Appropriate finning technique should reduce risk of reef impact, and can be selected to suit lateral or vertical proximity. Understanding the ecological effects of reef contact and knowledge of the vulnerabilities of local species allows avoidance of particularly vulnerable organisms, and is likely to motivate ecologically responsible divers to apply more effort to avoiding contacts. Adjusting proximity to suit sea conditions – clearance between diver and benthos can be adjusted to allow acceptable risk of contact for variations in surge and current. Low impact diving training Scuba training should be done where it has no direct impact on the environment if possible Diamond Reef "rollercoaster" course layout for low impact skills training and evaluation Low impact diving training has been shown to be effective in reducing diver contact. Strategies for sustainable use management Wreck diver keeping clear of the wreckage while swimming through an fairly confined space Several methodologies have been developed with the intention of minimising the environmental impact of divers on coral reefs Carrying capacity approach, where the number of divers is restricted. This also limits tourism income from the region. Sustainable diver carrying capacity is influenced by factors which vary between sites. These include coral morphology, presence of vulnerable species, environmental awareness and competence of the divers, presence of other stressors, size of the dive site, reef topography, and sea conditions. Continuous adjustment may be necessary to account for changes, unknowns and inaccurate models. Limits of acceptable change. This model uses quantitative limits on change defined in specific management objectives for a site using an established baseline. It does not handle natural variation well if this is unknown, and cannot distinguish between causes of change, some of which may be unrelated to diving. In some cases an undisturbed baseline may not be available. Percentile approach: This method considers a need for multiple reference sites and establishes trigger values quickly by comparing the extent of coral damage between dived sites and similar non-dived control sites. The trigger for management action is if the median abundance of damage to coral equals or exceeds the 80th percentile of damage at the reference sites. Limitations to this system include sensitivity to initial conditions - it does not work well if the reference sites are already significantly degraded, and permanent moorings tend to concentrate damage to the region near the mooring, it may pick up false positives from damage from non-diver causes, and it is sensitive to conditions at the control sites. Restricting recreational divers to delimited locations, which usually concentrates divers and damage along diving trails. This creates paths of degraded reef through the more pristine areas, and will cause customer dissatisfaction as the trail degrades further. Regulating the type of diving equipment allowed, generally accessories which are thought to increase reef contacts, such as gloves and cameras. These restrictions are understandably unpopular with photographers, and may be applied to both divers who manage to avoid contact and those who do not. Cost and complexity of photographic equipment does not correlate well with diving competence. Changing the methods by which the industry provides services: Closer supervision and intervention by dive guides can reduce diver contact rates where the divers are sufficiently skilled to modify their behaviour during the dive. It does not address basic incompetence, which is common. A pre-dive briefing on responsible behaviour, regulations and environmental values can reduce the rate of diver impacts where the divers are sufficiently competent to avoid contact. Experience was not found to be a strong indicator of competence, but inexperience and lack of regular or frequent practice are generally good indicators of poor buoyancy and trim skills. More effective interventions occur when the ratio of divers to guide is low. Diver carrying capacity Sidemount diver trimmed well to avoid contact with the bottom on a temperate granite reef in False Bay near Cape Town The number of dives over a time interval that results in an acceptable and stable level of degradation depends on a combination of factors that vary between sites. These include the presence of vulnerable organisms, and the stresses to which they are specifically vulnerable, the level of environmental awareness and responsibility of the divers, the diving skills and situational awareness of the divers, prevalent water conditions during dives, including currents and surge which increase difficulty of positional control, other anthropogenic stressors that may be present, and may combine their effects with diver impact, topographical details which affect diver maneuvering and risk of impact, and the size of the site. Continued periodical re-assessment will generally be necessary, even when there are no obvious large changes to external circumstances. These factors may vary considerably even within a specific ecological zone, and may be expected to be very different between for example, a tropical coral reef dominated by branching stony corals on a gradually sloping bottom with persistent moderate wave action and continuous current, in an area far from major industry, and a high profile granite corestone temperate reef with deep gullies and steep ridges, dominated by kelp, ascidians and echinoderms, and with seasonal variations in prevailing wave direction near a large industrial city. The appropriate equipment and relevant skills will also vary, and unfamiliar rental equipment can require some practice before the diver can use it well, particularly for optimising weighting and trim. Divers in training can not be expected to perform at their best while distracted by learning new skills, and this is also a factor to be considered as a potential stressor if there is no separation between training sites and sites for qualified divers.
D
Diver kicking up the sand with wash from the fins Diver kneeling on the sand in the Comores, note the dangling instrument combo Diver feeding fish at Cod Hole
A
Diver kicking up the sand with wash from the fins
A
Diver kneeling on the sand in the Comores, note the dangling instrument combo
A
Diver feeding fish at Cod Hole
A
Diver with negative buoyancy standing on coral structures on Guam
A
Diver trimmed head up produces downwash vortices while finning which lift bottom sediment.
A
Diver with dangling instrument console, which could impact the bottom or even get snagged on a reef
D
Diver with dangling instrument console, which could impact the bottom or even get snagged on a reef
D
Diver trimmed head up produces downwash vortices while finning which lift bottom sediment.
D
Wreck diver keeping clear of the wreckage while swimming through an fairly confined space Sidemount diver trimmed well to avoid contact with the bottom on a temperate granite reef in False Bay near Cape Town
A
Wreck diver keeping clear of the wreckage while swimming through an fairly confined space
A
Sidemount diver trimmed well to avoid contact with the bottom on a temperate granite reef in False Bay near Cape Town