How to measure the load on our ecosystem?

As part of a scientific project, KELLER level recorders are used to monitor the condition of mangrove forests on Aldabra Atoll in the Seychelles. It is part of the research program of the University of Zurich, which aims to assess the impact of global changes on biodiversity.

The problem of an increasingly rapidly changing environment threatens biodiversity in different parts of the world. The University Research Priority Program (URPP) seeks to better understand these consequences by observing various ecosystems and their relationship with climate change and local environmental conditions. One of the goals is to identify specific indicators that will allow better forecasting of future global changes if combined. Scientists from different disciplines work together on a number of long-term projects worldwide to get a complete picture of this trend and possible correlations. This requires collecting a large amount of data. Often, extensive fieldwork is needed to collect samples or study wildlife, while other parameters can be monitored automatically.

Mangrove thickets are located in shallow waters inside the lagoon. Water level and salinity are measured in the two largest zones.

A Delicate Wonder of Nature

One of the reference habitats is Aldabra Atoll, part of the island nation of the Seychelles, located in the Indian Ocean off the coast of Africa. This nature reserve, listed as a World Heritage Site, stretches 35 km and has no permanent inhabitants. Aldabra was included in the program as a model of a pristine ecosystem, virtually untouched by human activity. Moreover, it is highly vulnerable to the effects of rising

Sea level in most areas does not exceed eight meters above sea level. The reefs forming its base are distinguished by a diversity of marine flora and fauna. The largest population of giant tortoises in the world shares the slender ring of land with huge colonies of seabirds. Most of the islands are covered with shrubs and meadows. The coastal zone is dominated by rocky shores with several remarkable white beaches, while the sheltered inner areas are partially covered with mangrove thickets.

Aldabra Atoll - a unique habitat of many endemic species, listed as a UNESCO World Heritage Site. © G. Schaepman

Mangrove Yoga and Data Collection

Annabelle Constance participates in URPP GCB scientific projects related to Aldabra. She grew up in the Seychelles and has been studying the ecosystem of these islands since 2015. She is currently doing this as part of her doctoral dissertation at the University of Zurich under the supervision of Professor Gabriela Schaepman-Strub. The main goal is to predict how this system will behave under future changed conditions in order to take measures to preserve its unique nature. Annabelle works closely with the Seychelles Islands Foundation (SIF), which manages the reserve and supports scientific work in the area.

Since one of the serious consequences of climate change is sea level rise, this is also one of the main research directions on Aldabra. Mangrove thickets consist of shrubs and small trees adapted to grow in coastal salty or brackish water. They directly depend on fluctuations in water level and composition and are a promising indicator of habitat condition. Annabelle and the SIF team have already surveyed more than 1000 trees across the atoll and will continue monitoring them in the coming years. Scientists jokingly call this exhausting fieldwork "mangrove yoga." To link the development of mangrove forests with changes in surrounding water, accurate data on water level and salinity are needed. Therefore, the group installed level recorders throughout the coastal zone. They had to be durable and reliable. The Swiss company KELLER, specializing in pressure sensor production, provided twelve level recorders necessary for the scientific project.

Annabelle Constance

PhD Student

Faculty of Evolutionary Biology and Environmental Studies

University of Zurich

"I am glad that the staff at KELLER helped me choose the right solution for my project. Reliability and low maintenance costs are key factors for environmental monitoring."

Reliable Level Measurement in the Field

After a thorough assessment of the device requirements and the environmental conditions at the site, a suitable solution was found in collaboration with specialists from KELLER. Data loggers of the DCX-22AA-CTD series record water level, temperature, and electrical conductivity, which corresponds to salinity. This allows distinguishing water level changes related to tides from those caused by precipitation.

Measurement data are collected autonomously and stored in internal memory. The level meter uses two sensors: a submersible one for measuring the level and one located above the water surface for measuring atmospheric pressure.

Subtracting the current atmospheric pressure ensures that the level measurement is independent of weather changes and highly accurate. This allows detecting the slightest changes in sea level. Since the equipment is constantly exposed to a saline environment, it must be corrosion-resistant. Therefore, all external parts are made of titanium to ensure long-lasting and reliable operation. Additionally, the electronics were specially modified to increase memory capacity considering the complexity of regular access to the loggers. This allows the logger to record all three parameters for several months before reaching maximum memory capacity.

 NIFF staff transporting equipment over rough terrain ©URPP

KELLER level loggers were installed in protective setups by Annabelle and her team. Since late 2019, they have been taking measurements every 10 minutes and providing valuable information for the scientific program, Annabelle’s doctoral dissertation, and for SIF management in planning daily activities in the Aldabra reserve. In the long term, the data obtained from this scientific work will help preserve fragile ecosystems, counteract damage caused by climate change, and possibly play a role in saving our shared habitat on the planet.

Annabelle with a ready logger setup in mangrove thickets ©SIF

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