Extensive Coverage of Marine Mineral Concretions Revealed in Shallow Shelf Sea Areas

Laura Kaikkonen,Elina A Virtanen,Kirsi Kostamo,Juho Lappalainen,Aarno T Kotilainen

doi:10.3389/fmars.2019.00541

Laura Kaikkonen, Elina A Virtanen + Show 3 more

Open Access

https://doi.org/10.3389/fmars.2019.00541

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Abstract

Ferromanganese (FeMn) concretions are mineral precipitates found on soft sediment seafloors both in the deep sea and coastal sea areas. These mineral deposits potentially form a three-dimensional habitat for marine organisms, and contain minerals targeted by an emerging seabed mining industry. While FeMn concretions are known to occur abundantly in coastal sea areas, specific information on their spatial distribution and significance for marine ecosystems is lacking. Here, we examine the distribution of FeMn concretions in Finnish marine areas. Drawing on an extensive dataset of 140,000 sites visited by the Finnish Inventory Programme for the Underwater Marine Environment (VELMU), we examine the occurrence of FeMn concretions from seabed mapping and use spatial distribution modelling techniques to estimate the potential coverage of FeMn concretions. Using seafloor characteristics and hydrographical conditions as predictor variables, we demonstrate that the extent of seafloors covered by concretions in the northern Baltic Sea is larger than anticipated, as concretions were found at ~7000 sites, and were projected to occur on over 11 % of the Finnish sea areas. These results provide new insights into seafloor complexity in coastal sea areas, and further enable examining the ecological role and resource potential of seabed mineral concretions.

Highlights

Mineral precipitates found on the surface of soft bottom seafloors are ubiquitous in the world’s oceans
Our study focuses on the Finnish marine areas in the northern Baltic Sea, characterized by shallow, brackish water and a salinity gradient from north to south, with heterogeneous seafloor and a myriad of islands (∼100,000)
We have shown that ferromanganese concretions are common and abundant in the northern Baltic Sea, and that topographical and hydrographical parameters provide a solid basis for predicting their occurrence in coastal sea areas

Summary

Introduction

Mineral precipitates found on the surface of soft bottom seafloors are ubiquitous in the world’s oceans. Mineral precipitates come in many shapes and sizes, and according to their shape, they may be referred to in many terms. Common precipitates include polymetallic nodules or crusts, whereas their shallower shelf sea counterparts are often referred to as concretions, irrespective of their shape. In many coastal sea areas, the term ferromanganese concretion is established to underline the high concentration of these elements in shallow-water precipitates. Despite the widespread occurrence of shallow-water concretions, considerably more research effort has been invested in studying the distribution of Distribution of Coastal FeMn Concretions deep-sea nodules (Gazis et al, 2018; Peukert et al, 2018b; Alevizos et al, unpublished), with only scattered observations of shelf sea and coastal concretions (EMODnet Geology, 2019)

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