Mesophotic habitats, hosting benthic assemblages totally unknown and unexpected in the early 2000s, are attracting an increasing interest from scientists. Realizing that many long living and habitat forming species are playing a unique pocket of biodiversity in the frame of climate crisis, it is important to recognize the potential of the mesophotic zone in conservation strategies. The mesophotic zone is characterized by environmental factors generally more stable than the shallow counterpart; therefore, it represents a refuge habitat to preserve species that, in shallow waters, may be involved in bleaching events, massive mortalities or other pathologies generally triggered by thermal anomalies. The definition of the mesophotic zone in the temperate seas is confused, creating possible misunderstandings and problems not only from a scientific point of view but also in communication and outreach strategies. Here, we review the scientific literature to build the best definition possible based on the maximum consensus coming from papers analysis. Moreover, the key roles of mesophotic habitats, including ecosystem engineers as animal forests, have been schematized to enhance the perception of the potential risks we are running in case of damage or loss of these habitats.

Sponges are key components of the benthic assemblages and play an important functional role in many ecosystems, especially in coral reefs. The Indonesian coral reefs, located within the so-called “coral triangle”, are among the richest in the world. However, the knowledge of the diversity of sponges and several other marine taxa is far from being complete in the area. In spite of this great biodiversity, most of the information on Indonesian sponges is scattered in old and fragmented literature and comprehensive data about their diversity are still lacking. In this paper, we report the presence of 94 species recorded during different research campaigns mainly from the Marine Park of Bunaken, North Sulawesi. Six species are new for science and seven represent new records for the area. Several others are very poorly known species, sometimes recorded for the second time after their description. For most species, besides field data and detailed descriptions, pictures in vivo are included. Moreover, two new symbiotic sponge associations are described. This work aims to increase the basic knowledge of Indonesian sponge diversity as a prerequisite for monitoring and conservation of this valuable taxon. Sponges are key components of the benthic assemblages and play an important functional role in many ecosystems, especially in coral reefs. The Indonesian coral reefs, located within the so-called “coral triangle”, are among the richest in the world. However, the knowledge of the diversity of sponges and several other marine taxa is far from being complete in the area. In spite of this great biodiversity, most of the information on Indonesian sponges is scattered in old and fragmented literature and comprehensive data about their diversity are still lacking. In this paper, we report the presence of 94 species recorded during different research campaigns mainly from the Marine Park of Bunaken, North Sulawesi. Six species are new for science and seven represent new records for the area. Several others are very poorly known species, sometimes recorded for the second time after their description. For most species, besides field data and detailed descriptions, pictures in vivo are included. Moreover, two new symbiotic sponge associations are described. This work aims to increase the basic knowledge of Indonesian sponge diversity as a prerequisite for monitoring and conservation of this valuable taxon.

The series of technological advances that occurred over the past two decades allowed photogrammetry-based approaches to achieve their actual potential, giving birth to one of the most popular and applied procedures: structure from motion (SfM). The technique expanded rapidly to different environments, from the early ground-based and aerial applications in terrestrial scenarios, to underground and underwater surveys. Nevertheless, the transfer through different media required a period of adaptation that could take anything from years to decades. Only recently, thanks to the emergence of low-cost versatile imaging systems, have airborne and underwater photogrammetry became approachable to a wide range of research budgets, resulting in a popular cost-effective solution for many disciplines. Although numerous review efforts have already been made to resume the current knowledge on photogrammetry, this review summarizes the evolution of the technique in both terrestrial and underwater environments, paying special attention to the transfer of methods and techniques between the two environments. The acquired information helped to identify trends during its development and to highlight the urgency to widen the range of its applications in aquatic habitats in order to fill the current gap of knowledge on their structure and species distribution, delaying the design of proper conservation strategies.

Coastal areas are known to receive significant anthropogenic inputs, mainly deriving from metropolitan areas, industries, and activities related to tourism. Among these inputs, some trace elements are listed as priority pollutants in the European Water Framework Directive, due to their ability to bioaccumulate in organisms. Many studies have been conducted on heavy metals (HMs) accumulation and on their possible effects on different edible marine species. While the most studied sessile organisms are bivalves, in the current review, we focus our attention on other sessile taxa (sponges, cnidarians, bryozoans, polychaetes, cirripeds, and tunicates), proposed as bioindicators in coastal shallow waters. Although their potential as bioindicator tools has been repeatedly highlighted in the literature, these organisms are still poorly investigated and considered for monitoring. In this context, we analyze the available literature about this topic, in order to summarize the current knowledge and identify possible applications of these organisms in a bioremediation scenario.

Chalinula nematifera (Porifera: Haplosclerida) is an encrusting sponge able to overgrow live corals. It was described from the Western-Central Pacific Ocean and recently has been reported along the Mexican Pacific coast, where it is considered introduced and a potential threat for corals. However, there is a lack of accurate data about the distribution and abundance of Chalinula nematifera. Here we report a first wide assessment of its effect on different coral species and its growth rate. This is a first knowledge baseline for C. nematifera, based on visual and photo surveys, along the eastern coast of the Sulawesi Island (Indonesia).

The discovery of the association between the sponge Desmapsamma anchorata (Demospongiae: Poecilosclerida: Desmacididae) and the octocoral Carijoa riisei (Cnidaria: Alcyonacea: Clavularidae) on an Indonesian reef enlarges the widespread dispersion of these Atlantic species in the Indo-Pacific area. The species involved and their morphological adaptations resulting from the association are described. When covered by the sponge, C. riisei develops an irregular branching pattern and a dense nematocyst layer where the ectoderm comes in contact with the sponge tissue. The finding of fertile colonies suggests that the Indonesian population of C. riisei is self-sustaining.