Description: Giant kelp forests, with their extensive vertical structure, represent the most diverse of the marine habitats and support commercial fisheries, education, and recreation. Kelp forests/beds are dynamic, with substantial variability in extent of surface canopy between years associated with storms and other oceanographic conditions (e.g., El Niño Southern Oscillation). Although many functional values are tied to the presence of kelp canopy, habitat values persist in the absence of canopy (e.g., understory and bottom-dwelling algae, invertebrates, and cryptic fish species). Therefore, constraints maps in this document are based on historic occurrence and substrate.Kelp plants are vulnerable to vessel impacts (propellers, anchoring) resulting in frond entanglement or dislodgement of holdfasts. Kelp forest and associated understory vegetation also are sensitive to changing light levels and are limited when light transmission is substantially impaired. Light reduction does not have an impact on adult plants with surface canopies, but can reduce establishment of early life stages and growth of juvenile plants. Therefore, turbidity from sand management is of potential concern if substantial or prolonged. Kelp forests are highly vulnerable to sedimentation impacts, which can potentially damage plants from abrasion and scour or preclude recruitment when sediment accumulates on hard substrate. Kelp forests primarily occur outside the littoral zone, but may experience sedimentation during high wave conditions (e.g., storms, El Niño). Inshore boundaries of kelp forests, which may extend to shallower waters during mild oceanographic conditions, are most vulnerable to sedimentation and dislodgement during storms.Understory kelp occurring inshore of kelp forests are adapted to the relatively harsh environmental conditions in the littoral zone, including sedimentation. However, inshore kelp requires hard substrate for attachment; therefore, persistent sedimentation may lead to habitat degradation or loss. Long-term impacts would not be expected from transient sedimentation given the opportunistic life histories of many inshore kelp species.Sediment management impact considerations for kelp forests/beds include:§ Potential for substantial sedimentation based on sand volume and proximity of kelp forests/beds;§ Potential for prolonged turbidity over kelp bed areas; and§ Potential for equipment damage from vessels and anchoring.
Copyright Text: KTU+A Landscape Architecture & Planning, San Diego Nearshore Habitat Mapping Program (http://nearshore.ucsd.edu/), San Diego Association of Governments (SANDAG)