Underwater Seascapes

The emergence of underwater and marine areas is a gradual, ongoing process. It has gained speed in recent years particularly with “underwater landscapes”, which illustrate and stem from shared concern to manage marine areas. Yet, reference to the “underwater landscape” has merely been an echo to artistic or scientific currents of thought: confined to a handful of individual or original initiatives in specific fields, there has been no sufficiently substantial basis to allow any development. Bringing into perspective certain sequences relative to its emergence and formation will consolidate a reference base for greater expression and consideration of this geographic emergence of underwater landscapes and areas, having regard for what it reflects.

The implantation of the new national park in the Marseilles Calanques requires a juridical framework to protect these exceptionally attractive coastal and underwater landscapes. In order to analyze the reasons behind the spectacular nature of these submerged landscapes, it is essential to evoke the geological and climatic specificity of this coastal karst, submerged at the end of the last glaciation. The keys to understanding these formations are the lithology, the intense fracturing and intersecting of the massif determining coastal dissections and the eustatic factor. Besides these geological factors, the underwater landscape bathes in fluctuating light linked to the instability of winds and tides. The biological occupation completes the makeup of an underwater landscape specific to the Marseillse region. The Marseilless example demonstrates that underwater landscapes are the result of interlocking reasons, from the fundamental and determining geological structuration to the adaptive modalities of biological and human occupation, from the prehistoric artists of the partially submerged Cosquer cave to wrecks from the last war and Antique wrecks excavated by archaeologists.

In 1999 William B. F. Ryan and Walter C. 3rd Pitman suggest in their book: “Noah’s Flood: The New Scientific Discoveries about the Event that Changed History”, that the Black Sea, once a much smaller land-locked freshwater lake, was deluged about 7,500 years ago with salty water destroying the fertile plains around the once-shallow freshwater lake. For them, this would have happened when sea levels rose beyond a Bosporus critical point letting the Mediterranean Sea overflowed into the Black Sea basin. In this, Ryan and Pitman proposed that such a catastrophic event is likely to have remained in the collective memory leading to the creation of the story of Noah and the great flood. Since then, a vigorous debate arose between researchers in this region and the scientific community. As this debate concerns more the question of flood myths that are common in many early cultures, most of concerned researchers get to a point where they can’t see the wood for the trees meaning they did not consider the scientific results obtained from observations collected by a series of expeditions and showing that outside the cultural concerns, the Black Sea encountered a late major sea level rise during the Holocene. Here a synthesis on the assessment of the last sea-level rise in the Black Sea is presented. Numerous underwater surveys had collected data which interpretations evidence recent submerged landscapes somewhere around—100 m depth on the western Black Sea shelf consistent with a major low stand level witnessing that the Black Sea shelf was emerged at the beginning of the Holocene. Such important collections of data bring highlights to the debate regarding the precise timing and amplitude of the reconnection between the Black Sea and the Mediterranean Sea about 9,000 years ago.

Underwater landscape nowadays becoming a field of action for landscape designers: Politicians and natural marine parks are starting to resort to it. Contrary to what we could think, not only do landscape designers set up the land, they also carry out researches seeking to understand how a natural and/or cultural landscape can be seen by an audience, and managed at its best. They “read” the landscape. They can rely on science, but above all, this reading is for them an art; the art of “immersion.” Intuitively, artistically, graphically soaking up the place’s atmosphere bringing a new look upon it, understanding and conveying its emotion and specificity: this is the modern practice used by the French landscape designers of the Versailles school. However, can these methods, usually terrestrial, be applied to the underwater landscape? Do underwater characteristics (which are completely different from the terrestrial ones, starting with the visual water filter that questions an essential part of the definition of landscape itself) impose a change of method? What new tools and practices does the landscape designer have to invent in order to study the underwater landscape, and eventually act on it? The development of this quite new job is allowing new and unseen management perspectives for underwater landscapes. The landscape designer (alongside scientists), beside knowledge and protection, can facilitate coexistence between delicate marine environments and the audience, in terms of sensitization, cultural mediation, underwater museography, adjustments, and communication tools that are attractive and fitted into landscape. “Make understand rather than defend”: The “ecology of perception” is a substitute to the purely protective ecology present in the exotic laboratory of underwater landscape. All of this is, once out of the water, in favor of the terrestrial landscape to which we might have gotten accustomed too easily and not see all the beauty it offers us…

The perception of landscapes is expressed through practices and uses, as well as through social and cultural representations. In the case of underwater landscapes, this perception has a very specific history associated with the technical developments of deep-sea diving and the exploration of the sea bed. This exploration, which dates mainly from the 20th century, is a recent development in the history of humanity, relayed in contemporary media, in particular the cinema and the comic book. We discuss here the interplay between underwater landscapes and the comic book, to put a new slant on the way our contemporaries view landscapes.

This article is based on the results of a preliminary survey carried out with divers to analyse what the underwater landscape means for them. It aims at defining the contours of this concept in terms of their experience and their mental representations. Without claiming to offer an in-depth response to this question, this article sets out to establish a better understanding of the relationship between man and the accessible part of the underwater world, by defining the ways in which this specific environment is grasped, especially through the experience of landscapes it offers—from the understanding of their material and physical nature, to sensations and emotions involved—drawing on those who have first-hand knowledge of these subaqueous spheres—underwater divers. We will first discuss the precise terms of the survey itself, before going on to show how usage of the concept of underwater landscape is indeed replete with meaning for divers, by shedding light not only on the different connotations and denotations the term has for them, but also on the experiences it offers.

Several concepts revolve around the term “marine landscapes”: all of them are nourished by aggregating data from multiple sources and disciplines. The SINP (Système d’Information sur la Nature et les Paysages) is the French marine biodiversity and landscape building block in the global marine data infrastructure pyramid. Within this information system marine landscapes have been apprehended in both a pictorial and an ecological manner, therefore the usages of the SINP depend on the adopted definition. Through examples we argue that by increasing the availability of the massive volumes of cross-domain data necessary for apprehending landscapes, regardless of the chosen definition, the SINP can play a role in defining and refining our understanding of marine landscapes.

Macrophyte-formed habitats are important components of coastal temperate seascapes. They usually host higher diversity and density of fishes, including both adult and juvenile individuals. Here we synthesized the ecological processes underlying differences in fish assemblage structure among habitats, with an emphasis on the effects of habitat architectural complexity, which results in great part from the state of macrophyte assembalges. At a wide spatial scale, oceanographic patterns affect larval survival and dispersal and consecutive broad patterns of juvenile settlement. At a finer spatial scale, architectural complexities of the habitats affect their quality (basically food availability and predation risk) which drives local patterns of juvenile abundances through differential mortality and active habitat selection. Hence, the analysis and understanding of juvenile/adult abundance patterns have to consider nested sets of seascape features.

Intertidal zone is a marine area which can be reached easily at low tide periods and consequently allows observation at the landscape scale, much larger than that of the subtidal zone. Then an intertidalscape approach can be developed, particularly on the rocky shores where a macroalgal and faunal zonation based on emersion rates help the understanding of structure and evolution of the ecosystem. In this paper, we give the baseline of a new approach of intertidalscape ecology from examples on the Brittany rocky shores and particularly by developing a visual index (Intertidalscape Boulder Field Index, IBFI) using the opportunistic behavior of the green macroalgae to characterize the hand-fishing impacts on the boulder field habitat of the low eulittoral zone, on the rocky shores of Brittany, France.

ROV 3D project aims at developing innovative tools which link underwater photogrammetry and acoustic measurements from an active underwater sensor. The results will be 3D high resolution surveys of underwater sites and landscapes useful to keep in memory cultural and natural heritage. The new means and methods developed aim at reducing the investigation time in situ, and proposing comprehensive and non-intrusive measurement tools for the studied environment.

In this paper, we are presenting a new method of 3D surveys which are dedicated to high resolution modeling of underwater sites. The main met constraints in situ are taken into account and this method leads to a precise 3D reconstruction. Some examples will present both the main obtained results and their limitations. We will end with the perspectives and the necessary improvements to the method, so as to automate the multimodal registration step.

This paper presents application of multi-sensors data fusion to underwater landscape modeling.

It first deals with multi-sensors mini-oceanographic survey unit devoted to sea bottom mapping and monitoring developed by SEMANTIC TS. Then it presents research tasks conducted by SEMANTIC TS to develop a mapping method for underwater seabed. First stage is to develop methods for characterizing vegetation and sediment on the seabed using the acoustic response from a conventional single beam echo sounder. These new methods are then operated simultaneously with multi-beams sonar producing micro-relief information and side scan sonar providing gray scale levels associated with bottom reflectivity. Then fusion of these data is processed. We show efficiency of these multi-sensors survey unit and multi-sensors data fusion concepts to get very precise 3D bottom mapping allowing monitoring, in a way optimizing truth control (video and diving investigations). Examples are given on diving spot places showing results of these methods for underwater landscape modeling.

Services provided by coral reef ecosystems are now highly altered by natural and anthropogenic disturbances. The integrated management of marine biodiversity hotspots relies on the description and the evolution of reef landscape at various scales. The network of Polynesia mana ensures punctual and biennial recovery monitoring of Scleractinian corals at a decametric scale resolution over seven countries and territories located in the central area of the South Pacific. Despite the wide regional coverage of such a monitoring, the structure and dynamics of the outer reefs cannot be continuously described. Very high resolution remote sensing overcomes this shortcoming and provides spatial digital models of bathymetry and benthic albedo at 0.5–0.6 m resolution. The synergy of the two methods allowed (1) the structure of Tiahura outer reef (case study, Moorea, French Polynesia) to be represented, (2) the temporal fluctuations that occurred between 2006 and 2010 to be elucidated, and (3) the impact of the joint proliferation of predator Acanthaster planci and Cyclone Oli to be identified. Coherence and complementarity of in situ and satellite data encourage its extension to other sites in the network and its application in the study and management of reef landscapes.

Landscape ecology is a multidisciplinary field that combines the spatial approach of geography with functional ecology. Concerning marine environment, a submerged landscape, called seascape, is defined as a spatially heterogeneous area of coastal environment (i.e. intertidal, brackish). Measurement of spatial patterns plays a central role in monitoring environmental change and for studying the multi-scale processes that drive organism distributions and biodiversity. The aim of this paper is to propose a relevant seascape index focusing on Mediterranean littoral areas, moreover rocky habitat that constitutes one of the most important and characteristic habitats of the north-western Mediterranean coastal areas. The methodology proposed to score marine sites addresses three factors: biological, geomorphologic (i.e. 3D complexity) and anthropogenic. The goal was to build a functional and relevant tool that could eventually be used for a large scale geographical analysis of submarine landscapes along the north-western Mediterranean coast. The proposed index can qualitatively assess the value of the seascape within a site. Statistical tests showed that the proposed index is an accurate and relevant proxy of the seascape complexity value. The seascape integrity index we developed can then be a new tool that could complement other existing biological indices.

The LIMA index conveys the environmental interest and quality of the landscape formed by the Mediterranean benthos, ranging from 0 to − 40 m, in numerical format. The LIMA index allows a comparison spatially and temporarily between sites. It is a comprehensive index which is easy to implement and is composed of two factors: a topographical description (classification of 15 typologies) and a biological description (the presence or absence of some thirty species or groups of structuring, remarkable and invasive species). The LIMA index has been validated in the Bay of Calvi (Corsica-France) where it varies between 0.31 and 0.79 on a scale of 0.00–1.00.