Snorkelling and trampling in shallow-water fringing reefs: risk assessment and proposed management strategy

Abstract

Shallow reefs (reef flats <1.5 m) in the northern Red Sea are impacted by growing tourism that includes swimmers, snorkellers and reef walkers but have largely been neglected in past studies. We selected a fringing reef along the lagoon of Dahab (Sinai, Egypt) as a model for a management strategy. Point-intercept line transects were used to determine substrate composition, coral community and condition, and the coral damage index (CDI) was applied. Approximately 84% of the coral colonies showed signs of damage such as breakage, partial mortality or algal overgrowth, especially affecting the most frequent coral genus Acropora. Questionnaires were used to determine the visitors' socio-economic background and personal attitudes regarding snorkelling, SCUBA-diving and interest in visiting a prospective snorkelling trail. Experiencing nature (97%) was by far the strongest motivation, and interest in further education about reef ecology and skill training was high. Less experienced snorkellers and divers--the target group for further education and skill training--were those most prepared to financially support such a trail. We therefore recommend a guided underwater snorkelling trail and restricting recreational use to a less sensitive 'ecotourism zone' while protecting the shallow reef flat. Artificial structures can complete the trail and offer the opportunity to snorkel over deeper areas at unfavourable tide or wind conditions. This approach provides a strategy for the management and conservation of shallow-water reefs, which are facing increasing human impact here and elsewhere.

Fig. 1

Location of the study area. Left: Gulf of Aqaba, northern Red Sea, and the Sinai Peninsula, Egypt. Bottom: study area at the Napoleon Reef (Dahab, Gulf of Aqaba); dotted line: course of reef crest; rectangles: area 1 and 2, where transects were deployed. Top right: Ten plots (each 50 × 50 m or 40 × 50 m) subdividing the study area.

Fig. 2

Frequency [%] of pooled substrate categories (sand; live substrate: algae, hard coral, soft coral; dead substrate: coral rock, dead coral, dead coral with algae, rubble; broken corals: broken coral colony and fragments) in the “nearshore”, “intermediate” and the “offshore” areas (according to the three clusters of transects as revealed by the cluster analysis) at Napoleon Reef (Dahab, Gulf of Aqaba).

Fig. 3

Abundance (number of colonies) of partial mortality (PM) categories (no PM = 0%, PM 1 = < 25%, PM 2 = < 50%; PM 3 = < 75% and PM 4 = > 75%) across A: families, B: genera (others, each with n < 40: Astreopora, Cyphastrea, Favia, Favites, Goniastrea, Leptastrea, Millepora, Platygyra, Pocillopora and unidentified genera) and C: Acropora species (others, each with n < 20: A. acuminata, A. digitifera, A. hyacinthus, A. loripes, A. secale, A. subulata and unidentified Acropora). Values above bars indicate proportions (in %) of the respective taxon among all taxa.

Fig. 4

Coral damage index (CDI) of ten reef plots at Napoleon Reef (Dahab, Gulf of Aqaba). CDI represents the average frequency (%) of broken coral colonies (BCC) or coral rubble (RB) of all transects within each plot. The grey and the black lines indicate the threshold value for a “hot spot” within the BCC and the RB category, respectively.

Fig. 5

Motivation for snorkelling and diving and interest in environmental education. A: Motivations for snorkel- and SCUBA-dives (n = 318). advent. = adventure, meet.ppl. = meeting people, soc.cont. = social contacts. B: Interest in further education and training relating to a snorkelling trail (n = 318). Posed questions (a–g): (a) Offering environmental education courses for snorkellers/divers is sensible; (b) A briefing in snorkel skills before visiting a snorkelling trail is sensible; (c) A briefing in proper behaviour before snorkel/dive trips for reef protection is sensible; (d) A snorkelling trail is one reason for me to choose a snorkel site; (e) Offering environmental education courses for snorkellers/divers is one reason for me to choose a dive centre; (f) Offering environmental education courses for snorkellers/divers promotes business for dive centres; (g) A well-trained guide leading a snorkel trip on a snorkelling trail is sensible.

Fig. 6

Proposed course for a snorkelling trail (A) and prevailing direct human impact (B) at Napoleon Reef next to the lagoon of Dahab (Gulf of Aqaba, Egypt). A: natural pinnacles (black circles), proposed artificial structures (white circles) and an example for a snorkel trip along the underwater snorkelling trail (black line with arrows). Trail length measures about 150 m one way; depths refer to mid-water level; tidal range ± 0.4m (nip tide) ± 1.0m (spring tide). B: directions and areas of frequent direct human impact caused mainly by snorkellers, fishers and surfers (black double arrows).