A Short Review of Strategies for Augmenting Organism Recruitment on Coastal Defense Structures

Abstract

The global demand for coastal urbanization is rising with the increasing population. Alas, living close to the ocean threatens human endeavors with high currents, waves, and increasing storm frequency. Accordingly, the need for more coastal defense structures (CDSs) rises. Structures built from complex units meant to prevent and/or mitigate coastal erosion and floods, additionally providing wave protection or wave attenuation, are constructed on and near natural habitats where they alter local ecosystems. Traditional CDSs mostly fail to harbor diverse and abundant communities. However, this can be changed by eco-friendly methodologies and designs that are being tested and implemented to improve CDSs’ ecological value. Some of these can be implemented during the construction period, while others can fit on existing structures, such as wave breakers and seawalls. Effective methods include augmenting surface rugosity through strategic perforations, integrating artificial panels for increased complexity, implementing soft (naturally based) engineering solutions such as geotextiles, replacing industrial concrete mixtures for CDS construction with “green concrete” and ecologically friendly mixtures, and using alternative, eco-friendly units in CDS erections. In this mini review, we suggest that by integrating sustainable practices into coastal development, we can significantly mitigate the ecological damage caused by traditional CDSs and promote more harmonious relationships between human construction and the marine environment. This shift towards environmentally conscious coastal defenses is essential and a responsibility for ensuring the long-term sustainability of our coastal communities and the health of our oceans. We present current methodologies used on breakwaters worldwide.

1. Introduction

Coastal zones are highly populated environments that constitute various economic activities [1]. These include human settlements, harbors and shipping, fishery industries, aqua- and mariculture, power and desalination facilities, communication infrastructures, recreation and tourism, soil run-off and coastal erosion, and flood defense structures on or near the shoreline [2]. Concurrently, shallow marine coastal environments constitute diverse ecosystems that also provide critical ecologic and economic services, such as coral reefs, fish nursery habitats, oyster reefs, seagrass beds, and wetland and mangrove habitats [3,4]. The total value of these services was estimated at USD 1.25 × 10¹⁴ trillion per year [5,6]. Nowadays, due to the increase in flooding frequency, storm frequency, changing currents, sediment transport, sea level rise, shore erosion, and anthropogenic activities, coastal defense structures are being placed across vast sections of natural coastlines [7,8].

Coastal defense structures (CDSs) are designed to prevent coastal erosion and floods by mitigating wave energy, currents, and other marine forces. They can be onshore or offshore, constructed from various materials (such as concrete, wood, steel, plastic, sand, and quarry rock), and are configured to meet specific objectives. Onshore CDSs, like sea dikes, revetments, and seawalls, are built at the coastline, protecting shorelines’ coastal infrastructure (Figure 1, [9]).

Offshore CDSs, like breakwaters, jetties, and groynes, are built to protect coastal areas from waves and currents and prevent shore or estuary erosion (such in the case of jetties). They can start on land and extend into the water or be built directly offshore (Figure 1). Artificial islands, built mostly for commercial and economical functions, act similarly to offshore CDSs [10].

CDS construction can significantly alter natural marine environments, both physically and biologically. Physical changes include substrate modification, altered currents and wave patterns, and sand and silt erosion or accumulation, which can cause coastline erosion [3,11]. These can disrupt or enhance biological processes like colonization, recruitment, survival, reproduction, and dispersal [12]. Previous studies reported that CDS establishment resulted in habitat loss for local marine communities [13], disruption of species life cycles, loss of native species assemblages (alga, invertebrates, and benthic species), and attraction of invasive species due to the creation of these modified habitats [14].

On the other hand, establishing some CDSs (including breakwaters) has created new habitat opportunities. Due to their structural complexity (providing shelter and additional hard substrates [15]) and changes in sedimentation, currents, and habitat morphology, some CDSs have increased local biodiversity and species richness [16,17,18].

In Taiwan, Viyakarn et al. (2009) [19] demonstrated that live coral cover on breakwaters was similar to that at nearby natural reefs. Moreover, fish communities around the breakwater were as abundant and diverse as at the natural reefs, with only a few absent species. They suggested that these fish species could not inhabit the artificial structures due to the absence of structural elements, such as rubble and sand [19].

With that, establishing marine fauna on CDSs does not necessarily replicate and augment local communities. Studying coral settlement in the Azores archipelago, Martins et al. (2009) [20] found significant differences in species assemblages between a new breakwater and a nearby natural rocky habitat. Algae dominated the breakwater, while the natural site had more barnacles. This shift changed the ecosystem based on filter feeders into one dominated by producers.

Predicting the ecological effects of CDSs on marine habitats, reducing negative effects, and promoting ecological integration are crucial for coastal management but remain challenging due to numerous variables [12]. Over the past three decades, there has been rising interest in research and commercial endeavors for fostering biological and ecological enrichment through the deployment of CDSs [21]—a practice referred to as reconciliation ecology [22].

These efforts aim to turn habitats lost due to construction into thriving ecosystems, benefiting organisms like bivalves, oysters, mussels, and corals while providing coastal protection. This mini review will present and discuss current solutions, focusing on the ecological enhancement of breakwaters achieved through specialized eco-friendly construction materials and designs [23].

2. Breakwaters

2.1. Background

Breakwaters present an appealing research area due to their prevalence, accessibility, durability, and long-lasting nature, lasting up to hundreds of years. Breakwaters can be built close to or far from the shore, and even underwater (Figure 2).

Traditional breakwaters are constructed mostly from local or quarry-originated boulders of different sizes. Modern breakwaters are mostly made of concrete units of different types, such as antifers, accropode, cubes, dolos, tetrapods, and more [24,25]. Quarry-originated boulders are usually characterized by smooth surfaces [26] and, as such, are less suited for sessile organisms, such as bivalves and corals, that prefer to settle on porous and coarse surfaces [27]. The same applies to concrete units used in modern breakwaters, where special chemical treatment is added to strengthen and smooth the unit’s surfaces.

2.2. Low Recruitment Rates to Breakwaters

The chain of ecological succession in benthic marine habitats starts with microorganisms settling on the substrate, creating microbial and microalgal biofilms or mats [28,29]. Further stages follow with the settlement of more larger sessile species (both calcifying algae and mollusks), creating an additional 3D biogenic layer to the original substrate, thus called “habitat-forming species” [30]. The ongoing recruitment of organisms will then attract grazing and predatory species, consequently establishing a new community in the habitat [31]. If local conditions are less favorable for those crucial habitat-forming species, the natural recruitment chain will demise, leading to low biodiversity and species abundance [32,33].

However, where one struggles, another prospers, and often, invasive species take advantage of the new habitats and niches created by breakwaters and the low competition by local species found in them. CDSs’ individual units are relatively simple in shape and, as mentioned, have surfaces that are less fit for recruitment [14,27]. In cases where the natural source of larvae is far from the breakwater (such as in large, sandy areas), local species may fail to settle in the new habitat, allowing invasive species that are better suited for such niches to recruit on the breakwater and take advantage of the new habitat [34].

Breakwaters rarely foster diverse fauna or support a large community of species, contingent on their ability to recruit species [20,35,36]. An extensive examination of breakwaters’ impact on local ecosystems, testing breakwaters in Spain, Italy, Denmark, the UK [37], and Thailand [19], showed lower overall species richness on breakwaters compared to natural rocky shores. In Taiwan, Wen at al. (2010) [38] examined the reasons for differences between natural habitats and breakwaters. They found that due to the breakwaters’ alteration of the intertidal habitats, many local species, mainly reef-associated species, did not occupy the artificial structure, leading to a decline in local biodiversity.

This relatively low biodiversity is due to the simple fact that the breakwaters’ purpose is to protect human endeavors from sea stressors and not function as a habitat. They are built with hard structural units [26], which mostly lack sufficient surface roughness and rugosity, and minimize the abilty of marine species to penetrate and attach onto them [39]. Further, quarry-based and concrete molded units lack complexity in spaces between the units. Construction favors using large units. Therefore, space between them is limited and relatively simple. The ongoing shift from tetrapods to anifers further reduces the structural complexity of the breakwaters. Habitat physical complexity has been observed as a primary factor in community composition as it influences predation mediation, the reduction in niche overlaps, and the provision of shelter for vulnerable small organisms [40]. However, in some cases, breakwaters made of natural rocks created complex environments resembling nearby rocky habitats, allowing colonization of similar organisms [12]. This led to a conjecture that the low settlement rates of breakwaters primarily affect the outer parts of a structure, while inner (sheltered) areas may support more diverse and abundant marine life [8,41]. Sherrard et al. (2016) [8] suggested that the inner areas of breakwaters may be shielded from stressors such as currents, waves, and sediment, resulting in high biodiversity and species abundance among both flora and invertebrate fauna.

The chemical compound of the unit’s material is another factor affecting the recruitment of organisms onto a breakwater. Most industrial cement mixtures have high surface alkalinity, making them a poor biological recruitment substrate [42]. This may limit settlement, as colonizing biotas, from bacteria to corals and even egg-laying fishes, have preferences regarding aspects of the substrate surface (i.e., texture, color, alkalinity, or specific attracting chemicals) [43].

2.3. Prevalent Solutions

Nowadays, researchers and commercial maritime companies aim to modify and increase the ecological value of breakwaters by implementing “ecological service enhancement” (ESE) solutions. Attempts are made to modify the breakwater substrate and make it more suitable for the recruitment of mobile species, such as fish [44,45], and the settlement of benthic species, such as bivalves [26] and corals [46], and are achieved in several ways (Figure 3):

a)

Altering the boulder surface by hole drilling, chiseling, and creating slots to break the smooth surface and provide the necessary roughness [47].

b)

Combining add-ons onto artificial structures such as engineered blocks or terracotta plates attached to the breakwater.

c)

Using soft engineering construction elements and units [48].

d)

Using ecologically friendly cement mixtures in unit construction [42].

e)

Creating new breakwaters or sections of breakwaters from environmentally friendly units.

Most studies on breakwaters’ ESE have been carried out along the coasts of temperate zones such as the Mediterranean, northern Atlantic, North American West Coast, and eastern Australia. These studies were driven by the research team’s financial capability, or the applicability of the methods examined. Here, we review several approaches and cases used for the ESE of breakwaters in the context of increasing sessile species’ biodiversity and abundance.

3. Ecological Enhancement Methods

3.1. Surface Rugosity

These methods physically alter the surface of the breakwater unit using mechanical tools to create holes, grooves, and slots to enhance structure surface roughness [49]. These alterations can be implemented at any stage of the structure construction, including on existing structures. They can be used in moderate and high wave energy environments, where attached features such as tiles and artificial rockpools might not be suitable. Although these approaches’ main advantage is their low cost, they can still be challenging for developing countries. In these instances, where the availability of electrical or mechanical tools might be scarce, the desirable alteration can be achieved using hand tools, such as chisels. These local considerations are crucial as many biological enhancement attempts fail due to insufficient funding, especially in developing economies, and unsubstantial research support [50,51].

Hall et al. (2018) [26] tested the technique of hole drilling and groove graving on two breakwaters on the UK coast. One was made from granite boulders and the other from limestone. After one year, new sessile species were recorded in the holes and grooves. In the granite breakwater, an additional six species were observed to colonize the holes alongside five more species in the grooves, while in the limestone breakwater, an additional five species colonized the holes and fifteen species colonized the grooves. This result led to an increase in both the biodiversity and abundance of sessile species in the breakwaters. However, the authors reported that the holes and crevices created did not fit all the local species as some could not physically fit into the holes drilled [26].

3.2. Unit Surface Complexity

In other studies, artificial small and complex concrete or ceramic elements increased the outer surface complexity of breakwaters or seawalls [32].

An example of such elements are artificial concrete block mattresses (ACBMs) designed by Econcrete and implemented in port Everglades, Florida, USA. These small artificial concrete units add structural complexity and water-retaining features to a CDS [52]. As with all modifications to breakwaters, these mattresses require the necessary strength and integrity to withstand the pressure on the wave breakers; therefore, they are limited to mainly low- to medium-wave environments. A more popular and widespread technique is the application of hardened tiles, such as the ones designed by Living Seawalls (Figure 2), that are bolted to the structural unit and are able to withstand heavy weather conditions.

Tile design considers various elements such as pits, grooves, crevices, and overhangs to increase the complexity to increase marine fauna settlement. Habitat complexity affects community structure as animals of different sizes utilize habitat spaces differently [53,54].

Loke and Todd (2016) [55] tested different tile designs on two seawalls in Singapore to determine the effect of complexity on community biodiversity, abundance, and structure. The two seawalls were separated as low- and high-tide areas. Three types of tiles were compared; concrete tiles represented different designs (simple and complex), and granite tiles represented the control as they mimicked the seawall surface. After 13 months, species richness was higher on the complex tiles at low tides at both sites. The results demonstrate that substrate complexity and type significantly influence species composition, with distinct assemblages observed across complex, simple, and granite substrates, as shown by high success rates (59.38–84.38%). Complex tiles showed a range of different-sized species that utilized different parts of the tiles according to their size and shape and therefore had a different community structure compared to the simple tiles and granite controls.

Another design consideration is retaining water during low-tide conditions. This is important in intertidal zones, where water retention is crucial for species survival and recruitment [56]. In an experiment in Sydney, Australia, five tiles with distinct characteristics were compared in their ability to enhance settlement onto a seawall. The results of a 24-month survey of 102 species were recorded across all tiles. Complex tiles with water-retaining abilities were favorited by the majority of organisms, with 100 species observed during the survey [57].

Complexity enhancement-oriented projects produce a blend of coastal engineering with ecological element solutions [23,42,58,59,60]. These allow researchers to investigate the effects and importance of different complexity factors on biodiversity, abundance, and community structure in harsh, artificial structures.

3.3. Soft Engineering

Global efforts are shifting from traditional hard engineering to soft engineering. Nature-based soft engineering aims to replicate natural conditions using either natural materials (such as sand) or materials of natural origin (such as fabric) and eco-engineering. One such solution, geotextiles, has become increasingly common [48]. Geotextiles are either woven or non-woven permeable fabrics or synthetic materials that can be used in combination with geotechnical engineering material (Figure 3). Geotextiles have a wide range of applications in breakwater; they can act as a filter or installation layer and even as a replacement for the rock fill of a breakwater by using geo-containers and “Geo-bags” filled with sand and/or rocks [61] and, as a result of their diverse applications, ensure the durability and resilience of geotextiles against environmental stressors like saltwater, UV radiation, and sand abrasion. Selecting the appropriate material for specific ecological and engineering conditions is a key factor for the long-term success of any geotextile project. However, the limited stability and heavy impact of geotextiles have led to questions regarding them being soft-type solutions.

Wetzel et al. (2011) [62] tested geotextile ecological performance in Germany by comparing the settlement of sessile organisms on woven fabric, non-woven fabric, and ceramic tile two years post-deployment. The results showed that woven geotextiles showed a similar species richness (9.6 compared to 10.4), mean abundance (428 individuals per 10 cm⁻² compared to 567), and biomass (0.33 g 10 cm⁻² compared to 0.47) to ceramic tiles (commonly used to represent natural hard substrates). Non-woven geotextiles were the only treatment in which abundance decreased and did not show growth of encrusting species. These findings emphasize the importance of surface rugosity and woven geotextiles as an alternative to hard structures.

3.4. Ecological Concrete Composition

Concrete marine structures face many physical-chemical challenges from different tidal regimes, currents, and the chemical composition of the sea. While erosion, wetting–drying, and freezing–thawing are some physical effects, exposure to sulfate, chloride, magnesium, and carbonic acid attacks are some of the possible chemical effects [63].

Chemical attacks can cause corrosion (chlorides react with the reinforcement steel inside the concrete), alkali–silica reactions (reactive silica in the concrete aggregates with the alkaline pore solution leading to a gel product, which expands, causing cracking and spalling), and sulfate attacks (external/internal sources of sulfate react with aluminate phases and calcium hydroxide in the concrete) [64]. To address these phenomena, companies have concentrated their resources on developing robust, resilient concrete mixtures rather than considering the ecological impact of their cement. Indeed, the chemical composition of concrete can influence parameters determining the type and diversity of microorganism settlement, such as roughness, pH, and hydrophilic/hydrophobic characteristics of the unit’s surface [65].

A range of studies examined modifications to concrete composition that maintain structures’ resilience while improving the settlement of marine organisms [66,67,68]. These used either supplementary cementitious materials (SCMs) or alternatives to concrete. Different alterations have been suggested (

Table 1. Concrete alteration methods and their biological effects.

Alteration	Specific Compound Used	Effect	References
Reduce surface alkalinity	A CEMI/GGBS concrete mixture	It was found that 50% CEMI/50% GGBS tiles aggregate significantly more Diatoms, green algae, and cyanobacteria biomass than 100% CEMI tiles after one month.	[67]
Reduce chemical leaching	PFA/GGBS concrete mixture	Increased biofilm coverage rate by double that of commercial concrete mixture.	[66]
Lower carbon footprint	Hemp fibers and recycled shell material in the concrete mixture	After 12 months of deployment in the intertidal environment, the hemp and shell concrete tiles supported significantly higher live coverage of marine organisms than the GGBS concrete.	[68]
Increase small-scale porosity	Usage of tuff boulders and cobbles instead of smoothed rocks in concrete aggregates	Increased coral recruitment.	N. Shashar—unpublished data
Increase iron availability	Iron dust in cement mix	Increased biofilm and algal growth.	N. Shashar—unpublished data
Minimize deterioration of concrete under seawater attack	Magnesium ion as a replacement of calcium in Portland concrete	The addition of MgCl2 to synthetic calcium silicate hydrate (C-S-H) lowers the pH value below 10.	[70]
Lower pH	Accelerated carbonization	Accelerated carbonization and additions of mineral admixtures considerably reduced alkalinity (lowest pH value was 8.57) and showed no harmful effect on the compressive strength.	[71]

); however, in [69], no differences were found in biofilm development or composition between five concrete compositions during 1 year of deployment at Port Haliguen, Brittany, France.

Marine “Portland concrete” is the dominant compound in breakwater construction and gradually covers increasing coastline sections [72]. Its mixture has a pH range from 9 to 13 before curing, creating a habitat favoring alkaliphilic organisms [73].

Sella and Perkol-Finkel (2015) [73] installed ecologically engineered concrete blocks on a newly insulted breakwater in Haifa, Israel. The units were manufactured from an ecological cement mix (ECOncrete^® Antifers—EA) with a lower surface pH than Portland cement. In addition, the unit’s surface was designed to include holes and slots to recruit sessile species. The biodiversity, abundance, invasive species rate, and overall community structure of both the sessile and fish communities were compared to an untouched breakwater section that functioned as a control. After 24 months, survey results showed increased biodiversity index (from 0.5–0.76 to 1.15–1.57) and abundance (34 species on the EA compared to 15 in the control), and a lower rate of one-third total invasive species recruitment compared to the opposite of two-thirds in the control [73].

3.5. Environmentally Friendly Units

A growing number of CDSs and coastal construction projects include environmentally friendly units as the core or a significant part of breakwaters. These include submerged reef-ball structures, which act as wave breakers, and artificial reefs (Figure 1; [46]). Reef balls are hollow, hemispherical-shaped artificial units designed to improve biological growth and coral reef or mangrove restoration while acting as a coastal protection structure [46].

In 1998, approximately 450 reef-ball units were placed in the Dominican Republic for shoreline stabilization, environmental enhancement, and ecotourism. Three years after their installation, during which hurricane Georges occurred (1998), the shoreline not only survived the erosion; it gained up to 8740 cubic meters of sand in the project area along a 250 m shoreline. This corresponds to an average increase in beach elevation of 75 cm across a 250 m long by 46.5 m wide area [74].

3.6. Shelter-Oriented Studies

The crypted, sheltered parts of breakwaters have been theorized to harbor higher diversity than other surfaces as they provide additional protection from outside stressors [8]. Sherrard (2016) [8] examined the outer and inner parts of groynes around Christchurch Bay, UK, and evaluated their marine fauna. The results showed that internal surfaces supported twice as many species of invertebrates and algae (20 species) as the external environment (10 species), particularly mobile species. There was, however, a higher mean percentage coverage of species found on external faces (53% ± 50%) than on internal faces (25% ± 61%), suspected to be due to the prevalent presence of Ulva spp.

Ben Natan [75] examined this theory on habitat-forming species; differences in niche-based distribution of coral on breakwaters were documented on an exposed breakwater in Eilat, Israel (Tur Yam; 29°51′49.07′′ N, 34°55′26.65′′ E). He assessed niches formed by breakwater boulders, categorized by the level of shelter they provide to coral colonies. A shelter/protection niche was defined as a physical barrier protecting the coral’s volume from the oncoming current. The niche levels examined were exposed (no protection), partially sheltered (one or two sides of the coral colony are sheltered), and fully sheltered (three or four sides are protected). Quadrat surveys, to determent coral’s overall percentage difference among niches, were conducted on the Tur Yam breakwater. Using a 20 × 20 quadrat, 10 random samples of each niche were taken (30 samples overall). The survey results revealed significant differences in coral coverage across these niches, with the highest coverage in semi-sheltered niches (ANOVA, p < 0.05, Figure 4), which were higher in both sheltered and exposed areas (Tukey HSD, p < 0.05).

4. Discussion

As human activities along shorelines increase, the construction of new coastal defense structures (CDSs) and the replacement of natural habitats with artificial ones are inevitable. Growing awareness of the ecological impacts of CDSs has heightened the demand for environmentally friendly engineering solutions, making ecological considerations a prominent factor in CDS design and planning. However, most efforts focus on enhancing future CDSs, leaving existing structures largely neglected [76,77]. While some initiatives, such as ECOncrete and “Living Seawalls”, have successfully modified existing CDSs to support local biodiversity, the sheer number of existing structures necessitates greater attention toward their ecological enhancement.

Whether addressing new or existing CDSs, the techniques outlined in this review must align with the dual objectives of maintaining CDSs’ primary protective function and enhancing ecological value. To achieve this balance, project planning should involve multidisciplinary teams, including coastal engineers, ecologists, and policymakers, ensuring that ecological goals complement structural integrity and shoreline protection.

Interest in environmental engineering and ecological enhancement within marine construction is growing globally [78]. The adoption of ecological directives, such as the EU Marine Strategy Framework Directive (2008/56/EC) [78] and Britain’s 25-Year Environment Plan (25YEP) [79], highlights efforts to incorporate ecological considerations into urban coastal development. These directives emphasize integrating nature-based solutions and sustainable practices into construction while mitigating the risks associated with traditional “grey” infrastructure. International bodies, including the UN and the World Bank, have also underscored the economic and ecological risks of conventional solutions, promoting financial and legislative support for green alternatives [79,80].

Despite these advancements, legislation often lacks the authority to enforce ecological measures, leaving ecological considerations dependent on the political and economic priorities of local councils and private stakeholders [81]. Although international organizations provide recommendations and guidelines, the absence of mandatory regulations means that ecological enhancements remain sporadic rather than standard practice.

For CDS ecological enhancement to become mainstream, it must transcend opportunistic projects and align with long-term community involvement, education, and management. Integrating ecological principles into coastal stewardship programs and training, as seen in Australia’s vocational courses on “Marine Habitat Conservation and Restoration”, can foster community support and project sustainability. Such initiatives not only educate stakeholders but also build local ownership of projects, ensuring their success over time. Moreover, collaboration between regional councils, local governments, businesses, and communities is vital for maintaining these projects and embedding ecological reconciliation into broader coastal management strategies [4,51,82].

5. Conclusions

The rising demand for coastal development is driving the construction of numerous coastal defense structures, often replacing natural habitats with artificial ones. Ecological enhancement methods can be incorporated into future projects and existing structures to reduce these adverse effects. These methods have proven effective in increasing biodiversity and ecosystem health.

Today, new approaches are being explored to streamline modifications to existing CDSs, leveraging their protected and often cryptic sections. Over time, cracks, pores, and crevices form in CDSs due to their proximity to one another, creating sheltered areas that facilitate recruitment [8]. Ecological service enhancement (ESE) techniques often mimic these natural processes to support early and rapid recruitment. Most ESE techniques focus on the exposed sections of CDSs, which are designed to withstand harsh conditions. However, developing tools for use on the inner, protected sides of the CDSs could be beneficial, as they are simpler to access, and they can replace and accelerate slow natural processes that are perceptive to stressors.

For broader adoption of these ecological techniques, eco-friendly engineering principles must be integrated into regulatory frameworks for future coastal construction and development. Without these regulatory requirements, minimizing the ecological impact of CDSs on coastal environments will be challenging. In this regard, practitioners and planners should be well versed in these methods.

With the global rise in environmental awareness, technological advancements, and strengthened alliances between engineers and marine ecologists, the vision of a greener, eco-friendly coastline is set in stone. The future of sustainable coastal defense lies in our ability to harmonize human needs with marine ecosystems, ensuring that our protective structures serve as both barriers and habitats. Together, we are laying the groundwork for coastlines that safeguard human endeavors while nurturing the ocean’s rich biodiversity.