Dr. Kenneth L. Heck, Jr.

Current Research Interests

Submerged Aquatic Vegetation Restoration via Seeds

Submerged aquatic vegetation (SAV) is declining globally and losses in the Gulf of Mexico have occurred in every state, with areal declines ranging from 20-100%. The economic significance of SAV habitat is great, owing to their highly valued ecosystem services and their importance as nursery areas for a wide variety of valuable finfish, shrimp and crabs. Despite the recognized importance of SAV meadows, we have yet to fully understand the specific suites of factors that sustain successful meadows in different geographical regions, and that permit restoration of SAV once conditions become more favorable for their reintroduction.

We believe it highly likely that efforts to restore SAV, specifically shoalgrass (Halodule wrightii) and tape grass,(Vallisneria americana), in the northern Gulf would be successful due to the biology and physiology of these two species. We believe shoalgrass restoration from seeds would be successful in the northern Gulf because it is a relatively opportunistic species, which grows rapidly and can establish itself both by seed and vegetative fragments. This is similar to that of eelgrass (Zostera marina), the temperate species that has been successfully restored by seeding appropriate areas. Restoration of tape grass,from seeds would be successful in the northern Gulf based on recent work in Virginia which indicated that seeds may serve as a source of bed recovery after stressful conditions have passed. Thus, the use of seeds to restore tape grass,beds could be a useful adjunct to natural recovery in oligohaline portions of northern Gulf estuaries.

The primary goal of the proposed research is to determine whether there is a sufficient seed reservoir for both SAV species that could be harvested with minimal damage to existing meadows, and, if so, whether restoration by seed planting is a locally viable SAV restoration strategy in the northern Gulf of Mexico and Mobile Bay. The proposed work is largely unproven to date, but the critical need to develop alternative restoration techniques, instead of the highly damaging and usually ineffective transplant methods, means that new and innovative approaches to restoration must be developed and tested.

Seagrass Restoration using Bird Guano

An increasing threat to seagrass is mechanical damage from motor vessel operation in shallow waters. This is a growing problem in most coastal areas as these areas are more frequently used for recreational activities. In Florida, and elsewhere in the Gulf of Mexico, physical damage by motor vessels is one of the most common human impacts to seagrass beds. Motor vessels are implicated in seagrass bed damage in a number of ways, including anchoring, propeller scarring, and large excavations caused by hull groundings. In 1995 it was estimated that 173,000 acres of seagrass beds in Florida were moderately to severely damaged by boat propellers and hull groundings (Sargent et al. 1995). Fortunately, reversing the seagrass loss in many of these cases can be done on a relatively small scale with public education and restoration (Kirsch et al. 2005; Hall et al. 2006).

Cost-effective techniques are needed to facilitate early intervention for the prevention of scar erosion to enhance seagrass restoration. Our fertilization technique utilizes a novel approach by providing nutrients derived from the feces of sea birds which are encouraged to roost on perches installed at the restoration site (Kenworthy et al. 2000, Hall et al. 2006). The bird roosting stakes are constructed of 1 in. PVC pipe with pressure treated 2 x 2 x 8 inch blocks glued to the top of the stakes. The stakes are pressed into the sediment so they are not submerged at high tide. Seabirds, primarily cormorants, terns, pelicans and blue herons, roost on the stakes and defecate nutrient rich feces which act as a passive fertilizer delivery system putting nutrients into the water and sediment surrounding the stakes.

Seagrass Monitoring

Recovery of seagrass and recolonization after losses are rare, and destruction of seagrass habitat may have long-term consequences for sediment stability and production of economically important finfish and shellfish (Williams and Heck 2001). For this reason, many coastal states with substantial seagrass resources assess the distribution and abundance of seagrass meadows annually.

We are carrying out an annual monitoring program, beginning in summer 2011, using a tiered monitoring approach to survey the seagrass resources in the Mississippi and Florida portions of the Gulf Islands National Seashore. The protocol is based on a hierarchical design in which “Tier I” monitoring includes aerial surveys, photointerpretation,, mapping and ground truthing. “Tier II” includes rapid assessment of the overall abundance and distribution of seagrasses, and “Tier III” includes long-term detailed monitoring at selected locations. Our effort is specifically for Tier II and Tier III work that is conducted during the summer when seagrass biomass reaches its annual maximum. Because Tier II monitoring is focused on seagrass percent cover and species composition, it has added value in providing ground-truthing data for Tier I as it becomes available from state or federal agencies. Tier III data are useful for evaluating the likely factors involved in explaining observed changes in seagrass maximum depth distribution, percent cover or species composition.

Climate-mediated ichthyofaunal shifts in the northern Gulf of Mexico: implications for estuarine ecology and nearshore fishery production.

Recent increases in global temperatures are expected to drive concurrent changes in the composition and ecology of terrestrial and marine communities worldwide. Therefore, information on the effects of climate change on marine ecosystems has been repeatedly identified as being critical for the proper implementation of adaptive, ecosystem-based management. However, few studies have quantitatively linked effects of climate change with shifts in regional fishery production. Recently, Fodrie et al. (2010, Global Change Biol) quantified changes in fish assemblages within seagrass meadows of the northern GOM between the 1970s and 2000s, and found that several tropical snapper, grouper and parrotfish species have become significantly more abundant over the last 30+ years. For instance, Lutjanus synagris (lane snapper) was entirely absent three decades ago, but is now the 8th most abundant seagrass-associated fish. L. griseus (gray snapper, now 7th most abundant), Mycteroperca microlepis (gag grouper, now 17th most abundant) and Nicholsina usta (emerald parrotfish, now 23rd most abundant) have also greatly increased.

Coastal seagrass meadows are well known to provide critical nursery habitat for many juvenile fishes and crustaceans that ultimately recruit offshore to highly valuable fisheries (Heck et al. 2003, MEPS). Therefore, there is a pressing need to explore how the changes documented by Fodrie et al. (2010) might affect seagrass nursery habitats in the northern GOM, as well as the very large fishery production that is ultimately and inextricably linked to this iconic nearshore habitat. Doing so is a necessary first step that will assist in the wise management of Essential Fish Habitat as climate continues to evolve.

Therefore, we are addressing the following 2 overarching questions: 1) how have climate-related changes affected the contribution of seagrass nurseries to economically valuable adult populations of snappers and groupers, as well as to endemic red drum and spotted sea trout; and 2) how are food webs in seagrass nursery habitats functioning in response to increases in tropical fish species? To answer these questions we are using both observational (population level) and manipulative (food-web level) approaches.

Shoreline Stabilization via Oyster Reef Restoration

Coastal and shoreline habitats like salt marshes, oyster reefs, and seagrass meadows protect coastal lands from waves and storms, provide shelter and food for many marine organisms, and supply food, occupation, and recreation for human societies. Unfortunately, many of these habitats are also among the most degraded and threatened habitats in the world because of their sensitivity to sea level rise, storms, and increased human utilization. Many previous efforts to protect shorelines have involved the introduction of hardened structures, such as seawalls, rocks, or bulkheads to dampen or reflect wave energy. A major concern in implementing bulkheads and seawalls for coastal property protection is that many nearshore habitats are damaged and destroyed because erosive wave energies are reflected back into the water body, instead of absorbed or dampened. Mobile Bay, like many other coastal areas, is highly developed with a large and increasing proportion of the shorelines armored by bulkheads and seawalls.

At last analysis in 1997, over 30% of the bay’s available coastline was armored with over 10-20 acres of intertidal habitat lost, a high percentage in this microtidal bay. A recent study found that historical armoring and marsh-edge losses have already had negative fisheries consequences, and projected further reductions of blue crab harvest if armoring continues. Recently, a growing initiative for sustainable shoreline protection has focused on balancing effective protection and habitat creation by a variety of new methodologies collectively termed “living-shorelines”. Wave-reducing breakwaters are becoming an increasingly common along sheltered coastlines and are proclaimed by many as a more responsible alternative to traditional shoreline armoring; however, their effectiveness or ecological impact is largely untested.

This project is designed to examine the potential benefit of restoration of shallow subtidal oyster reefs on adjacent nearshore habitats located at Point aux Pines and in the vicinity of Alabama Port, by examining whether such habitats will (1) result in fisheries enhancement; and (2) facilitate the maintenance and expansion of other biogenic habitats, by addressing the following four objectives:

1. documenting changes in the physical setting of study sites resulting from the addition of oyster reefs.
2. quantifying oyster recruitment and adult density in created nearshore reefs.
3. quantifying primary and secondary producers within subtidal and intertidal habitats between created oyster reef and shoreline.
4. quantifying juvenile and adult fish and mobile invertebrate utilization of created oyster reefs and adjacent habitats.

Lab Group