since the early 1980s. These blooms occur as the result of nutrient pollution and degraded water quality, and their growth is further stimulated by high temperatures. In 2016, the river experienced the flourishing of extensive algae blooms, along with Lake Okeechobee and the Caloosahatchee River. The cyanobacteria, or blue-green algae, causes numerous severe health consequences for the marine ecosystem as well surrounding human populations. Blooms result in reduced dissolved oxygen concentrations, alterations in aquatic food webs, algal scum lining the shores, the production of compounds that cause distasteful drinking water and fish flesh, and the production of toxins severe enough to poison aquatic as well as terrestrial organisms. Blooms have been reported throughout the continental United States, and resulting cyanotoxins have been associated with human and animal illness and death in at least 43 states. Most cyanobacteria produce the neurotoxin beta-N-methylamino-l-alanine (BMAA) that has been implicated as a significant environmental risk in the development of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Amyotrophic Lateral Sclerosis (ALS). The cyanobacteria has also been linked to liver cancer, chronic fatigue illness, skin rashes, abdominal cramps, nausea, diarrhea and vomiting. Metal contamination The ecosystem has proven to be contaminated with metals, especially benthic organisms. In 2014, it was determined that 86% of the river's amphipods and hard-shell clams contained copper and zinc concentrations higher than the threshold effect concentrations for Florida sediment quality criteria and the National Oceanic and Atmospheric Administration Screening Quick Reference Tables (SQuiRTs) sediment values. Strategies for improvement The South Florida Water Management District and its partners have put together various projects with the intention of improving the river and estuary: The St. Lucie River Watershed Protection Plan, CERP: Indian River Lagoon South (includes the C-44 Reservoir), CERP: Lake Okeechobee Watershed, Central Everglades Planning Project, Water Storage Strategies, Basin Management Action Plan, Herbert Hoover Dike Rehabilitation, Kissimmee River Restoration and Kissimmee Basin Modeling and Operations Study. St. Lucie River Watershed Protection Plan According to the South Florida Water Management District, this plan will address pollutant load reductions based on adopted total maximum daily loads (TMDLs). It will also include a goal for salinity levels and freshwater inflow targets for the St. Lucie Estuary. List of crossings This is the list of bridges crossing the river, starting with the North Fork, then going down the main river, and then jumping back to where the South Fork joins the North Fork