Reply to Zvuloni, A.; Shaked, Y. Comment on “Shashar et al. Artificial Reef Deployment Reduces Diving Pressure from Natural Reefs—The Case of Introductory Dives in Eilat, Red Sea. Oceans 2024, 5, 71–80”

1. Introduction

In a recent study [1], we describe how deploying a small artificial reef (AR) in an area experiencing heavy diving pressure shifted introductory dives (ID) away from the local coral nature reserve. The effect was preserved over more than 15 years post-artificial reef deployment. This finding emphasizes the potential use of planned artificial reefs as a conservation and stress-reduction tool for natural reefs. Zvuloni and Shaked commented [2] on this study and provided interesting and valuable insights as to factors affecting the fringing natural reef. In [2], they confirm and support the empirical findings of a shift in diving routes of introductory dives (ID) away from the fringing reefs in the Eilat nature reserve, following the deployment of a small artificial reef. However, they provide alternative explanations for the results. (1) Educational efforts by the Nature Reserves Authority, asking guides of ID stay outside of the nature reserve. (2) Decrease in the attractiveness of the natural fringing reefs due to cover by sand carried by floods, effects of low tides, and storms. They imply that planned ARs may suffer less environmental damage than natural reefs. Due to such differential damage, dive guides are likely to “prefer to lead the divers to the more beautiful and less damaged areas of the reef”. While these factors may contribute to changing dive patterns, our study, supported by recent social media data analysis [3], suggests that the artificial reef plays an important role in redistributing diving pressure, particularly for introductory dives and training dives.

2. Choice of Diving Routes and Alternative Dive Site

Following this comment [2], we went back to four dive club managers and owners to discuss with them the reasons for the shift in the routes of the ID, following the deployment of the AR. Dive club managers all stated that the AR is a focal point of ID. This is consistent with the findings of the original study and the routes of ID tracked. When asked for the reasons for this focal point, they stated that it is interesting, made with a friendly design for ID, and well-placed. When asked about educational activities of the Nature Reserve Authority to keep ID away from the marine protected area, two agreed that these may have some effect, one asked “what educational activities?” and one said “so what, we must go somewhere”. When asked what will happen if the AR was not in place, one said “we will spend more time on Outcrop 6” (inside the nature reserve, currently still visited), two said “we will go back to the fringing reef”, and one mentioned both Outcrop 6 and the fringing reef. These responses confirm the function of the AR as an alternative dive site to the natural fringing coral reef.

Recent studies demonstrated the value of social media data in a range of marine conservation contexts, such as monitoring marine recreational users [4], and assessing cultural ecosystem services of marine protected areas [5]. In line with these approaches, a social-media-retrospective data mining [3] offers additional insights into the AR’s role as an alternative dive site to the natural fringing coral reef. Analysis of 568 diving-related social media posts from 2014 to 2016 revealed that 25.7% (146) of posts originated from the Almog beach, where the Tamar AR is located, compared to 13.9% (79) from the neighboring marine protected area. This distribution suggests a noteworthy difference in diving activity between these two areas. Of the Almog beach posts, 26.7% (39 out of 146) were from dives led by an instructor, composed of 17.1% (25) introductory dives, 8.9% (13) course-related dives, and 0.7% (1) guided dive for a certified diver, with the rest being of certified unguided divers. In contrast, the marine protected area showed a different pattern, with only 2.5% (2 out of 79) of posts related to introductory dives.

These insights, derived from social media data, offer a unique perspective on diving patterns in Eilat. By capturing spontaneous diver behavior and interests, this approach provides a nuanced understanding of how artificial reefs, including small structures like the Tamar Reef, can influence dive site choices and potentially alleviate pressure from natural reefs. This method not only complements existing data but also addresses the monitoring concerns raised [2]. The ability to conduct retrospective analysis through social media data mining offers a cost-effective method for continuous monitoring of diving activities and their potential impacts on both natural and artificial reef environments.

Furthermore, this approach allows us to observe long-term trends and seasonal variations in diving activities, providing a more comprehensive understanding of the AR’s role in reef conservation efforts. The sustained interest in the Tamar Reef, as evidenced by its consistent appearance in social media posts years after deployment, supports our original findings of the AR’s long-term effectiveness in influencing dive patterns.

3. Effects of Natural Pressures and Disasters on the Reefs

The comment suggested that the attractiveness of the local fringing reefs declined due to a series of naturally occurring devastating events. A detailed description of such natural pressures, such as floods, extreme low tides, and storms is provided, stating that it decreased the attractiveness of the natural fringing reef [2] but not so for the AR; although the latter was exposed to the very same pressures, with the obvious exception of the effects of tides. Being part of a critique, this description is significant (as in the Bible, Numbers 24). It is of special value when provided by the ecologist of the Gulf of Aqaba of the Israeli Nature and Parks Authority—AZ, and the manager of the Israeli National Monitoring Program for the Gulf of Aqaba—Y.S. Although no empirical evidence for such disproportional decrease is provided, considering the authors’ roles and statuses, one should take their statements as reliable. Indeed, since its construction, the AR has gained biological complexity and attractiveness (Figure 1), possibly one of the reasons it remains attractive to ID over the years. The effectiveness of design features in maintaining artificial reef attractiveness has been demonstrated in other locations as well [6].

A full description of the AR structure is provided elsewhere [7]. Nonetheless, the AR was planned to withstand both sedimentation and strong water flow. It was built without cavities facing upwards or concaves where sand can accumulate, and its curves were set such that sand will flow down and away from the AR (Figure 2).

The structure itself was designed to allow water to pass through it, with large openings set throughout the AR. A simulation of water flow was made in 2019, in a flume Figure 3 left), on two full rows of OBS units (Figure 3 right, note the reported AR has only 6 units, as in Figure 2). It was found that flow attenuation and transmission for all tests had maximal values of 58% and 46%, respectively, including in the most severe situation. Further, wave reflection from rows of OBS units amplified much less than from a full structure. This means that the AR design, using the OBS units, attenuates the force of the flow passing through it, but still passes nearly half of the water, and therefore reduces the reflected wave and the forces experienced by animals living in it.

Another part of the comment states that it is possible that divers’ pressure on the natural reefs may increase due to advertisements for the AR. The data do not support such a trend related to ID and the fringing reef, nor is the AR posted on advertisements calling for performing ID in nearby clubs (strangely enough, it is featured on trash canisters in the city of Eilat). Presumably, this speculation refers to other types of divers which are outside the scope of the current paper. Nevertheless, it is worth stating that different types of divers affect the natural environment in different ways [8], and that different types of ARs may be needed to cater to their needs, to produce a wide range of alternative dive sites [9,10,11].

Recent social media data analysis provides further insights into this dynamic. While the AR attracts divers, it does not necessarily increase overall pressure on natural reefs. Instead, it appears to redistribute diving activity, with a notable shift in introductory dives towards the AR area [3]. This redistribution effect is particularly evident in the proportion of introductory dives recorded at Almog Beach (17.1%) compared to the Marine Protected Area (2.5%). Such findings suggest that the AR is effectively serving its purpose in providing alternative dive sites and potentially alleviating pressure on more sensitive natural reef areas, especially from less experienced divers who may have a greater impact on the marine environment.

4. Conclusions

Examination of additional diving activities is needed for improving the ability of ARs to reduce diving pressure from natural reefs [1,2]. The AR described [1] is a single case demonstrating the functionality of this management tool. We join the call [1,2] and urge for the deployment of new, planned, small ARs as measures for diver traffic control near natural reserves, to be accompanied by detailed scientific research. Careful design enables such ARs to withstand natural and anthropogenic disturbances at least as well as the local natural reefs.