SEA THE PROBLEM

What do they have to face?

Microplastics as a threat for coastal protection

This literature review synthesizes current research on the effects of microplastic pollution on the coastal-protection potential of salt marshes. Salt marshes trap sediments of all kinds and can accrete vertically under sea-level rise while reducing for example wave energy and, consequently, erosive forcing on coastlines, dikes, or other coastal-protection measures. However, sediments of all kinds also include microplastics (smaller than 5 mm) which alter the soil’s microbial community and its biogeochemical properties. It is evident that natural-based polylactic acid (PLA) tends to act as a fertilizer, whereas plastics like polyvinyl chloride (PVC), often mixed with a variety of additives, can be identified as the biggest threat to plant health. We found that small-scale laboratory experiments suggest that soil alteration caused by microplastics can be identified as a significant factor contributing to reduced plant growth and lower stress resistance of salt-marsh species. However, no large-scale modeling or natural observations are available to quantify these effects. This review highlights the urgent need for integrated modeling frameworks and long-term field studies to quantify how microplastics may undermine the role of salt marshes as nature-based coastal-protection solutions.

Saltwater intrusion as a threat to freshwater aquifers

Saltwater Intrusion (SWI) into coastal freshwater aquifers is a major challenge intensified by climate change.The climate related intensification of natural processes such as storms, floods and droughts lead to higher impact saltwater intrusion. At the same time, the freshwater aquifers are affected by human activities such as land-use change, groundwater extraction and other hydrological modifications that further weaken the coastal aquifers. These combined factors lead to lateral and vertical intrusion. The lateral SWI happens from the side when the hydraulic gradient between fresh water and saline water is decreased. Vertical intrusion occurs after inundation events from above or from below by upconing triggered by extensive groundwater pumping. Rising salinity alters chemical properties of the soil and water, disrupts ecosystems, reduces agricultural yields and threatens the drinking water supply of coastal populations. To counter these impacts, management strategies rely on technical and governmental measures. The measures can be split into different categories. There are structural interventions such as cut-off walls and subsurface dams aiming to stop the saltwater from intruding in the first place. Secondly there are measures to help the salt water discharge and recovery of the coastal aquifers like land reclamation, abstraction of salty or brackish water, reduction of fresh water pumping and desalination. Regulations on water and land use management can reduce the consumption of freshwater. As SWI is expected to intensify in the future, effective and adaptive management will be crucial, particularly for densely populated coastal regions that depend heavily on freshwater from coastal aquifers.

Compound Weather Events – Was passiert mit Ostfriesland?

Extreme weather events such as heavy rainfall and droughts are increasing worldwide as a result of climate change. In coastal regions, heavy rainfall and storm surges in particular pose significant risks. Their spatial, social, and economic impacts can be substantial. It is becoming increasingly evident that extreme weather events often occur in combination. Consequently, compound weather events are gaining attention in both policy and research. These events involve several extreme conditions occurring simultaneously or in close succession, including storm surges, heavy rainfall, sea-level rise, and river flooding. Risk assessments frequently focus on individual types of extreme weather. As a result, the overall destructive potential of compound weather events remains difficult to evaluate. This study models the hazard potential of the East Frisian coastal region between Emden and Wilhelmshaven. It also examines which combined extreme events are likely to occur in the future and what implications they may have for the population, infrastructure, and industry. The low-lying region is particularly vulnerable to storm surges from the North Sea and to flooding from the Ems River. Due to its elevation, East Frisia is often described as a “bathtub.” When storm surges coincide with heavy rainfall and river flooding, the region fills with water. Pumping and drainage systems reach their operational limits, and effective drainage becomes increasingly difficult. Political, infrastructural, and technical measures are therefore essential for East Frisia. Emergency plans need to be updated to ensure the protection of the population, and dike systems require further elevation. 

Marine Heatwaves: An overlooked Driver of Baltic Cyanobacteria Blooms?

Marine Heatwave (MHW)-Events have been growing in frequency and intensity in most regions of the world. The trends of these anomalous events in stratified marginal seas like the Baltic Sea have been studied extensively. At the same time an increase in Harmful Algal Blooms (HAB’s) was described by multiple sources for this region. While most studies describe increased nutrient input as the main driver of HAB’s, examples from global study sites have shown that these events are sometimes accompanied, and in rare cases even thought to be caused by MHW-Events. This study focuses on analyzing records of harmful cyanobacteria blooms and MHW-Events in the surface layer of the Baltic Sea using Sentinel-2 Data within the cloud-based platform Google Earth Engine (GEE). The goal is to investigate the correlation and influence between MHW’s and HAB’s finding time periods where both overlap. For this purpose, cyano- bacterial bloom intensity is quantified by calculating a Phycocyanin-Index and MHW- Events are detected by using Sea Surface Temperature (SST) for a Detection-Algo- rithm. [The results show that there is no significant correlation between MHW’s as a trigger for HAB’s. However, it could be argued that MHW’s act as a driver of already occuring HAB’s]. This is followed by a discussion about whether MHW’s could indeed be considered a notable driver of Cyanobacteria-Blooms in the Baltic Sea backed by already existing studies, research and literature.