ZMT - Leibniz Zentrum für Marine Tropenforschung

A group of sci­ent­ists from Leib­niz Centre for Trop­ical Mar­ine Re­sear­ach (ZMT), the Royal Neth­er­lands In­sti­tute for Sea Re­search (NIOZ) and MARUM – Cen­ter for Mar­ine En­vir­on­mental Sci­ences went to Cur­a­cao to gather data on the mod­ern and fossil reefs sur­round­ing the is­land. Their ex­ped­i­tion will last from Au­gust 23rd un­til Septem­ber 3rd, and they will use state-of-the-art ap­proaches to un­der­stand how reefs have re­spon-ded and will re­spond to warmer cli­mates and higher sea levels.

In parallel, they will also test low-cost instruments (such as portable sonars and drones) to develop simple (and fun) methods to gather high-resolution 3D data of nearshore ecosystems. The research team as a twofold goal. First, they are set out to acquire high-resolution data on coral reefs to understand their functioning today and in the past, with the hope of using this knowledge as a key to understand future changes. Second, they aim to develop a setup to generate reproducible nearshore data that can be used not only by scientists but also by  citizens at large, e.g. elementary school pupils. This citizen science approach, if successfully developed and implemented, may allow to document benthic dynamics in an unprecedented temporal and spatial resolution in nearshore environments. In the long run, this project will allow to acquire data to advance our knowledge on how reefs responded to climate change in the past, how they are responding today and how they will likely respond in the future.

Coral near Curacao | Photo: Fleur van Duyl, NIOZ

The research team as a twofold goal. First, they are set out to acquire high-resolution data on coral reefs to understand their functioning today and in the past, with the hope of using this knowledge as a key to understand future changes. Second, they aim to develop a setup to generate reproducible nearshore data that can be used not only by scientists but also by  citizens at large, e.g. elementary school pupils. This citizen science approach, if successfully developed and implemented, may allow to document benthic dynamics in an unprecedented temporal and spatial resolution in nearshore environments. In the long run, this project will allow to acquire data to advance our knowledge on how reefs responded to climate change in the past, how they are responding today and how they will likely respond in the future.

Coral reefs are one of the most valuable ecosystems on our planet. It is estimated that their global net value is 2.7 trillion US dollars, as they pr. Despite this immense value, we are witnessing a rapid, anthropogenically induced decline of coral reefs worldwide. It is estimated that human impacts and climate change together threaten approximately 75% of the world's coral reefs. We are at risk of losing the ecosystem services that coral reefs provide within the next 2 to 3 generations. An immediate scientific and conservation challenge is the facilitation of natural reef resilience in the face of global change. At the same time, relic reefs from ancient warmer periods of the Earth’s history are one of the best tools to understand past changes and frame possible future climate traject.

Back in 2013, the NIOZ-MARUM Tandem Cooperation was initiated with the aim of joining forces to understand the consequences of climate change and human impacts on the world oceans and coasts. Since then, Paolo Stocchi (NIOZ) and Alessio Rovere (MARUM) have started to use fossil corals to quantify tides and sea-level changes deep in the past. Using fossil reefs in the Caribbean and elsewhere as an analogue for a future warmer world, they understood that there is a growing need to model the dynamic interactions between coral reef organisms and ocean hydrodynamics (waves and tides). However, this requires the knowledge of micro-scale processes acting on much shorter time-scales than the usually long-term ones associated with climate changes. Paolo and Alessio quickly understood that their expertise alone was not enough to work on these problems. The presence at NIOZ of Fleur Van Duyl and the arrival of Andi Haas (formerly at San Diego State and Scripps, USA) brings the necessary "know-how" of experimental and theoretical approaches to turn early ideas into a novel research effort. The partnership with a researcher expert on gathering data on coral reefs with drones, Elisa Casella of the Leibniz Centre for Tropical Marine Research (ZMT), will also allow them to map selected coral reefs in Curacao with an unprecedented perspective and level of detail. The team is completed by Ciro Cerrone, a PhD student at the University of Napoli, currently working on a DAAD visiting grant at MARUM, who is expert on paleo sea level changes.

Quadrant (1x1 meter) of living coral at 10 meter depth near NIOZ buoy 2. | Photo: Fleur van Duyl, NIOZ

Understanding reef resilience

Curacao presents unique characteristics that make it the “one in a thousand” destination for the research team. First and foremost, the team will take advantage of unprecedented efforts by NIOZ scientists, who have created the longest available time series on coral reef benthic cover along the reefs Curacao and Bonaire. This time series, consisting of 24 permanent benthic photo quadrants has been documenting community dynamics across different water depths since 1973. A drastic decline in coral cover from 70 per cent to less than 10 per cent was recorded from 1973 until 2010. However, despite the devastating reports from many other coral reef locations around the world within the last decade, these Caribbean reefs showed a slight recovery from 2010 until now without tangible alleviations of the overall anthropogenic pressure they were subjected to. What are the underlying mechanisms of this resilience? Paolo, Andy, Fleur and Elisa will use drones, bathymetric surveys and different types of sensors to answer this question.

Second, Curacao has preserved fossil reefs from at least two past warm periods of the Earth’s history, when sea level was higher than today and the West Antarctic Ice Sheet was likely partially collapsed. Part of the research team will investigate these reefs to understand how they relate to their modern counterparts, in terms of both community and structure. How were the fossil reefs surviving in a warmer climate? Is it possible to understand past reef resilience by comparing data on the fossil reefs to their modern counterparts? How high was sea level during these past warm periods? To answer these questions, the geologists Alessio Rovere and Ciro Cerrone will survey the fossil reefs with the aim of characterising their composition, they will map their 3D extent with a drone and will establish their elevation with a highly accurate GPS system.

Methods and expected outcomes

The research team will use the Curacao expedition to test a series of affordable, portable and easy-to-deploy mapping systems. For example, Paolo will use a Stand Up Paddleboard connected to a fishfinder, a GPS and a GoPro camera to map shallow water reefs. Elisa will employ a portable and inexpensive drone (that was registered at the Curacao Civil Aviation Authority) to gather high-resolution 3D imagery of both modern and fossil reefs. The team hopes that this will be the first step towards setting up citizen science initiatives in Curacao, in order to foster the collection of an ever-growing base of highly needed data. Using cheap and portable modern technology to gather useful data at high spatial and temporal scales may prove transformative in understanding the many processes dictating the functioning, and the resilience of reefs.

The 2019 NIOZ-MARUM Expedition to the Curacao coral reefs was born out of the shared scientific interests of multiple PIs from different Oceanographic institutions, who joined both funds and expertise to start this collaboration:

• Paolo Stocchi (NIOZ COS) is a geophysicist whose expertise is in the numerical modelling of physical oceanographic processes.
• Alessio Rovere (MARUM, University of Bremen) is a marine geoscientist interested in reconstructing past sea-level fluctuations during warmer periods.
• Elisa Casella (ZMT, Bremen) is an environmental engineer specialized in using UAV platforms applied to the study of coastal environment and coastal changes
• Andi Haas (NIOZ MMB) is a marine biologist with a strong background in coral reefs biogeochemistry and ecology.
• Fleur van Duyl (NIOZ MMB) is a marine ecologists with close to unmatched knowledge on the ecosystem functioning of Caribbean reefs.
• Ciro Cerrone (DAAD Visiting PhD Student, MARUM) is a geologist working on paleo sea level changes.