Aquaculture America 2023

February 23 - 26, 2023

New Orleans, Louisiana USA


 Leo J. Fleckenstein, Jill C. Fisk, Andrew J. Ray,

School of Aquaculture and Aquatic Sciences

Kentucky State University Land Grant Program

Frankfort KY 40601 USA


Inland aquaculture systems using brackish-water often accumulate high levels of nitrate and phosphate due to limited water exchange. The effluent from these systems is often difficult to dispose of, as the high levels of salt make it unsuitable for fertilizer and many municipalities do not allow saline discharge into municipal sewer systems. Aquaponics may allow these aquaculture producers to remove nitrogen and phosphorous through plant production. However, there is a limited number of plants that have been shown to be successful in brackish water, many of which are halophytes that may be difficult to market due to consumer preference or unfamiliarity. Bell peppers (Capsicum annuum) are one of the most consumed peppers in the United States, with an average of over 5kg of peppers consumed per person in 2018. Bell peppers are also subject to a rapidly increasing trade deficit; in 2006 35% of bell peppers were imported and in 2021 75% were imported. Successfully producing peppers in brackish water may allow producers to reuse water while producing a high demand, locally grown product.

To test the salinity tolerance of bell peppers, fifteen 18L tanks were assigned in triplicate to 5 treatments: 0 ppt, 5 ppt, 10 ppt, 15 ppt, 20 ppt. Two plants were grown in each tank and were susupended using a polystyrene raft. LED grow lights provided 12-16 hours of illumination per day. Crystal Sea® Reef Crystals©, a commercial sea salt mix, was used to reach the taget salinity in each treatment, and each tank was fertilized with 50ml of a commercial hydroponics fertilizer. Water quality parameters (temperature, DO, pH, salinity, conductivity, total ammonia nitrogen, nitrite, nitrate, phosphate, potassium, and iron) were measured weekly.

As of this writing the study is still ongoing, however data was collected recently on day 24 of the study. CCI, height, number of buds, flowers, and peppers all decreased as salinity increased. Several instances of plant mortality have occurred at 15 and 20 ppt. No flowering has occurred at 15 or 20 ppt, however peppers at 5 and 10 ppt have flowered with no peppers currently present. Nitrate and phosphate uptake is significantly higher in 0 ppt compared to all other treatments. Iron uptake is significantly higher in 0, 5, and 10 ppt compared to 15 and 20ppt. Plants are also showing signs of light stress as salinity increases, along with increased cell lysis along leaf veins on the underside of the leaves. Future analyses will include ICP testing of both water and plant tissues to document nutrient dynamics.