Three common sampling techniques in Pleistocene coral reefs of the Red Sea: a comparison

Abstract

Line Intercept Transects (LIT), Point Intercept Transects (PIT), and Photoquadrats (PQ) are the most common quantitative sampling techniques in modern and fossil coral reefs. Data from coral reefs obtained by the different methods are generally compared between various reef ages and localities. Quaternary reefs from warmer interglacial periods, which represent climate scenarios projected for the future, are particularly interesting for comparisons with modern reefs. Importantly, fossil reefs differ from modern reefs because they are diagenetically altered and time averaged. While several studies have compared different quantitative methods in modern reefs, very few have dealt with the comparability among fossil and between fossil and modern reefs. Here, we compare LIT, PIT at 10, 20 and 50 cm intervals, and PQ in two Pleistocene reef localities in Egypt. We find that alpha diversity, reef cover and community composition are dependent on the method. Results gained with plotless methods (LIT, PIT) differ strongly from results gained with plot methods (PQ). However, coral cover results are similar between LIT and PIT, and community composition is indistinguishable between the two, but alpha diversity depends on the interval used for PIT. We discuss the implications of our findings for comparing coral reefs of various ages and localities. We recommend surveying Pleistocene reefs with PIT at 20 cm intervals. This is because A) alpha diversity is well captured, B) the amount of time averaging recorded by PIT is reduced compared to PQ, C) the PIT results can be directly compared to reefs analyzed by LIT, and D) the method is less time consuming than LIT and PQ.

Impact of Climate Change on Marine Coral Reef Communities

“…Fig. 1 Distribution of Coral Reef around the world (Pink coloured part is the coral reef) [1]. Known as undersea rainforest, coral reefs are one of the most diverse ecosystems in the world.…”

“…As in Figure 1, the pink part of the figure represents areas where coral reefs grow, occupying only a small fraction of the world's ocean area. "Coral reefs are found mainly in more than 100 countries and regions of the world, that reside in tropical and semi-tropical waters, but cover only 0.2% of the seabed [1]. " Healthy coral reefs support about 25% of the fish on the seafloor, as well as small organism species.…”

“…Sea level rise may also lead to changes in the salinity of seawater, causing corals to die as they fail to adapt in time. This has resulted in a massive die-off of shallow water coral reefs, "According to the IPCC, a record-shattering warming world of 1.5°C would mean a 70-90% decline in coral reefs [1]. "…”